[jdk11u-dev] RFR: 8254178: Remove .hgignore

[George Adams]

backports https://bugs.openjdk.org/browse/JDK-8254178 as it's a low-risk change

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Commit messages:
 - Backport 736e077335ec53c3804537a6abefa79087efd3ad

Changes: https://git.openjdk.org/jdk11u-dev/pull/1206/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1206&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8254178
  Stats: 16 lines in 1 file changed: 0 ins; 16 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1206.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1206/head:pull/1206

PR: https://git.openjdk.org/jdk11u-dev/pull/1206