Fix typos

This commit fixes the following build error:

```
Check spelling of all files with codespell: spec/rubocop/cop/style/redundant_exception_spec.rb#L120
valiable ==> variable, valuable, available
Check spelling of all files with codespell: spec/rubocop/cop/style/redundant_exception_spec.rb#L125
valiable ==> variable, valuable, available
```

https://github.com/rubocop/rubocop/actions/runs/6484903585

Author: koic

spec/rubocop/cop/style/redundant_exception_spec.rb

@@ -115,14 +115,14 @@
     RUBY
   end
 
-  it 'registers an offense for raise with RuntimeError, valiable' do
+  it 'registers an offense for raise with RuntimeError, variable' do
     expect_offense(<<~RUBY)
-      raise RuntimeError, valiable
+      raise RuntimeError, variable
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
     RUBY
 
     expect_correction(<<~RUBY)
-      raise valiable.to_s
+      raise variable.to_s
     RUBY
   end
 end