RFR: 8184352: Remove Sun provider information from KeyPairGenerator javadoc

[Ben Perez]

Removed algorithm-specific information from `KeyPairGenerator` class description and instead linked out to the Sun Provider documentation

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Commit messages:
 - Updated language on KeyPairGenerator class description

Changes: https://git.openjdk.org/jdk/pull/23280/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23280&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8184352
  Stats: 10 lines in 1 file changed: 0 ins; 6 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23280.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23280/head:pull/23280

PR: https://git.openjdk.org/jdk/pull/23280