test: add missing assertion for axios parameter property absence

Adds assertFileNotContains check for the axios parameter property
in erasable syntax mode to close the regression gap.

Author: darrell-thobe-sp

modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/axios/TypeScriptAxiosClientCodegenTest.java

@@ -210,6 +210,7 @@ public void testUseErasableSyntaxConfig() throws IOException {
                 TestUtils.assertFileContains(baseTsPath, "this.field = field;");
                 // Should NOT contain parameter properties
                 TestUtils.assertFileNotContains(baseTsPath, "protected basePath: string = BASE_PATH,");
+                TestUtils.assertFileNotContains(baseTsPath, "protected axios: AxiosInstance = globalAxios");
                 TestUtils.assertFileNotContains(baseTsPath, "public field: string,");
             } else {
                 // Non-erasable syntax: uses parameter properties