update akka-http and pekko-http server generator and example

[xuwei-k]

fix some warnings and update akka, pekko and scala versions.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[xuwei-k]

ActorMaterializer is deprecated

https://github.com/akka/akka/blob/4ab9d55102a1c9038950e1034ab3d34103e4a3dd/akka-stream/src/main/scala/akka/stream/ActorMaterializer.scala#L208-L209

https://github.com/apache/pekko/blob/ccb24f53b9f3c2bde48c2830fc18b4ff4a16f7c9/stream/src/main/scala/org/apache/pekko/stream/ActorMaterializer.scala#L222-L223

[xuwei-k]

bindAndHandle is deprecated

https://github.com/akka/akka-http/blob/a110fe9f4996c3ad96f16055917d816b454e15d3/akka-http-core/src/main/scala/akka/http/scaladsl/Http.scala#L218-L220

https://github.com/apache/pekko-http/blob/b529b645dba08b7d25d4019412273e4527f1f184/http-core/src/main/scala/org/apache/pekko/http/scaladsl/Http.scala#L241-L243

[xuwei-k]

avoid warnings

[warn] tmp/samples/server/petstore/scala-pekko-http-server/src/main/scala/org/openapitools/server/StringDirectives.scala:12:16: implicit conversion method _symbol2NR should be enabled
[warn] by making the implicit value scala.language.implicitConversions visible.
[warn] This can be achieved by adding the import clause 'import scala.language.implicitConversions'
[warn] or by setting the compiler option -language:implicitConversions.
[warn] See the Scaladoc for value scala.language.implicitConversions for a discussion
[warn] why the feature should be explicitly enabled.
[warn]   implicit def _symbol2NR(symbol: Symbol): NameReceptacle[String] = new NameReceptacle[String](symbol.name)
[warn]                ^
[warn] tmp/samples/server/petstore/scala-pekko-http-server/src/main/scala/org/openapitools/server/StringDirectives.scala:13:16: implicit conversion method _string2NR should be enabled
[warn] by making the implicit value scala.language.implicitConversions visible.
[warn]   implicit def _string2NR(string: String): NameReceptacle[String] = new NameReceptacle[String](string)
[warn]                ^
[warn] tmp/samples/server/petstore/scala-pekko-http-server/src/main/scala/org/openapitools/server/StringDirectives.scala:31:18: implicit conversion method apply should be enabled
[warn] by making the implicit value scala.language.implicitConversions visible.
[warn]     implicit def apply[T](value: T)(implicit sdef: StringDef[T]): StringMagnet { type Out = sdef.Out } =
[warn]                  ^
[warn] three warnings found

[wing328]

cc @clasnake (2017/07), @shijinkui (2018/01), @ramzimaalej (2018/03), @chameleon82 (2020/03), @Bouillie (2020/04) @Fish86 (2023/06)

[chameleon82]

Approved