Remove unnecessary files from @InputFiles

[ikhoon]

Motivation:

After upgrading Gradle 7, I can see the following warning for the
implicit dependency between checkScalafmt task and our resources
folder though they are not related each other.

Execution optimizations have been disabled for task ':scala_2.13:checkScalafmt' to ensure correctness due to the following reasons:
  - Gradle detected a problem with the following location: '/mnt/actions-runner/_work/armeria/armeria/scala/scala_2.13/gen-src/main/resources'.
  Reason: Task ':scala_2.13:checkScalafmt' uses this output of task ':scala_2.13:versionProperties' without declaring an explicit or
  implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed. Please refer
  to docs.gradle.org/7.1/userguide/validation_problems.html#implicit_dependency for more details about this problem.

Modifications:

• Use only formattable files as an @InputFiles

Result:

Clean up noisy warnings in Gradle 7