MINOR: Remove unnecessary license generation code in wrapper.gradle

[ijuma]

Newer versions of Gradle handle this automatically.

Credit to @granthenke for the tip.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[omkreddy]

@ijuma For testing, I removed gradlew and ran gradle wrapper. The newly generated gradlew does not have license header. not sure if this is the expected behavior.

[ijuma]

@omkreddy Are you sure? The diff for gradlew in this PR is after I did the same.

[ijuma]

If you look at older branches, we were generating two license headers:

c19266a#diff-36ffbd2ea7085cf19547193a7faf30c8

[omkreddy]

@ijuma Thanks for the PR. LGTM. earlier I was using older version of gradle (5.1.1) to generate wrapper. it was working with 5.6.2

[ijuma]

Makes sense. Thanks for being diligent!