RFR: 8341931: os_linux gtest uses lambdas with explicit capture lists

[Kim Barrett]

Please review this simple change to two lambdas in a gtest, to use the
preferred implicit reference capture rather than explicit capture.

Testing: mach5 tier1

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Commit messages:
 - use implicit ref capture instead of explicit capture

Changes: https://git.openjdk.org/jdk/pull/21513/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21513&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341931
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21513.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21513/head:pull/21513

PR: https://git.openjdk.org/jdk/pull/21513