RFR: 8316998: Remove redundant type arguments

[Mourad Abbay]

Remove cases of redundant type arguments in the java.util.stream package.

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Commit messages:
 - Remove redundant type arguments.

Changes: https://git.openjdk.org/jdk/pull/15936/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15936&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316998
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/15936.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15936/head:pull/15936

PR: https://git.openjdk.org/jdk/pull/15936