RFR: 8303175: (fs) Deprecate com.sun.nio.file.SensitivityWatchEventModifier for removal

[Brian Burkhalter]

Deprecate `SensitivityWatchEventModifier` for now instead of directly removing it as proposed in #12626.

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Commit messages:
 - 8303175: (fs) Deprecate com.sun.nio.file.SensitivityWatchEventModifier for removal

Changes: https://git.openjdk.org/jdk/pull/12746/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12746&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303175
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12746.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12746/head:pull/12746

PR: https://git.openjdk.org/jdk/pull/12746