RFR: 8263833: Stop disabling warnings for sunFont.c with gcc

[Phil Race]

As per the bug report the code that was the reason for disabling warnings on this file was removed in November 2019
as part of https://bugs.openjdk.java.net/browse/JDK-8220231 so we can get rid of the need to disable warnings.

Longer history in the bug report.

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Commit messages:
 - 8263833: Stop disabling warnings for sunFont.c with gcc

Changes: https://git.openjdk.java.net/jdk/pull/3081/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3081&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263833
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3081.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3081/head:pull/3081

PR: https://git.openjdk.java.net/jdk/pull/3081