[BUG][SCALA] Akka-client cannot be build agains scala 2.13.x version

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

I am trying to generate akka-client for scala 2.13 and it fails as it cannot find the underlying dependencies.

com.typesafe.akka/akka-http_2.13
org.json4s/json4s-jackson_2.13
org.json4s/json4s-ext_2.13
org.scalatest/scalatest_2.13
com.typesafe.akka/akka-stream_2.13
com.typesafe.akka/akka-actor_2.13
de.heikoseeberger/akka-http-json4s_2.13

openapi-generator version

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/scala-akka-client/build.sbt.mustache

(here your code)

(for YAML code) or

(here your code)

(for JSON code), so it becomes more readable. If it is longer than about ten lines,
please create a Gist (https://gist.github.com) or upload it somewhere else and
link it here.
-->

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

Update above dependencies to below;

  "com.typesafe" % "config" % "1.4.1",
  "com.typesafe.akka" %% "akka-actor" % "2.5.24",
  "com.typesafe.akka" %% "akka-stream" % "2.5.24",
  "com.typesafe.akka" %% "akka-http" % "10.1.9",
{{#joda}}
  "joda-time" % "joda-time" % "2.10.1",
{{/joda}}
  "org.json4s" %% "json4s-jackson" % "3.6.7",
  "org.json4s" %% "json4s-ext" % "3.6.7",
  "de.heikoseeberger" %% "akka-http-json4s" % "1.27.0",
  // test dependencies
  "org.scalatest" %% "scalatest" % "3.0.8" % "test",
  "junit" % "junit" % "4.13.1" % "test"

Start with modules/openapi-generator/src/main/resources/scala-akka-client/build.sbt.mustache and compare its dependency declarations with the Scala 2.13 dependencies listed in the issue. Generate an akka-client project and check whether its dependencies resolve for Scala 2.13.x. Done means the generated build uses compatible dependencies and builds successfully.