RFR: 8231735: gradle checkrepo is obsolete and doesn't work with git

[Kevin Rushforth]

https://bugs.openjdk.java.net/browse/JDK-8231735

This removes the obsolete `checkrepo` and `checkrepoall` gradle tasks. They use a script which assumes Mercurial support, and so no longer run. Also, with `git jcheck` support now available, these tasks are no longer needed.

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Commits:
 - 3b44a0d4: 8231735: gradle checkrepo is obsolete and doesn't work with git

Changes: https://git.openjdk.java.net/jfx/pull/2/files
 Webrev: https://webrevs.openjdk.java.net/jfx/2/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8231735
  Stats: 26 lines in 1 file changed: 0 ins; 26 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/2.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/2/head:pull/2

PR: https://git.openjdk.java.net/jfx/pull/2