[Java] checkstyle - fix license

[asfimport]

Make header correspond to the defined Apache license in checkstyle.license

Reporter: Bryan Cutler / @BryanCutler
Assignee: Bryan Cutler / @BryanCutler

PRs and other links:

• GitHub Pull Request #2816

_{Note: This issue was originally created as ARROW-3588. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 2816
#2816