Revert "[kotlin-client] Add support for integer enums in serialization for kotlin-client (OpenAPITools#21248)"

This reverts commit 0aaeb45.

Author: 4brunu

modules/openapi-generator/src/main/resources/kotlin-client/enum_class.mustache

@@ -43,45 +43,20 @@ import kotlinx.serialization.*
 {{#allowableValues}}{{#enumVars}}
     {{^multiplatform}}
     {{#moshi}}
-    {{#isString}}
     @Json(name = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
-    {{/isString}}
-    {{^isString}}
-    @Json(name = {{{value}}})
-    {{/isString}}
     {{/moshi}}
     {{#gson}}
-    {{#isString}}
     @SerializedName(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
-    {{/isString}}
-    {{^isString}}
-    @SerializedName(value = {{{value}}})
-    {{/isString}}
     {{/gson}}
     {{#jackson}}
-    {{#isString}}
     @JsonProperty(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}}){{#enumUnknownDefaultCase}}{{#-last}} @JsonEnumDefaultValue{{/-last}}{{/enumUnknownDefaultCase}}
-    {{/isString}}
-    {{^isString}}
-    @JsonProperty(value = {{{value}}}){{#enumUnknownDefaultCase}}{{#-last}} @JsonEnumDefaultValue{{/-last}}{{/enumUnknownDefaultCase}}
-    {{/isString}}
     {{/jackson}}
     {{#kotlinx_serialization}}
-    {{#isString}}
     @SerialName(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
-    {{/isString}}
-    {{^isString}}
-    @SerialName(value = {{{value}}})
-    {{/isString}}
     {{/kotlinx_serialization}}
     {{/multiplatform}}
     {{#multiplatform}}
-    {{#isString}}
     @SerialName(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
-    {{/isString}}
-    {{^isString}}
-    @SerialName(value = {{{value}}})
-    {{/isString}}
     {{/multiplatform}}
     {{#isArray}}
     {{#isList}}