RFR: 8339271: JDK-8328999 giflib update removed giflib VCS URL

[Alisen Chung]

Changing format of file paths in giflib copyright file and removing extra text from authors list

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Commit messages:
 - update md file

Changes: https://git.openjdk.org/jdk/pull/20859/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20859&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339271
  Stats: 16 lines in 1 file changed: 6 ins; 10 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20859.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20859/head:pull/20859

PR: https://git.openjdk.org/jdk/pull/20859