[jfx17u] RFR: 8290527: Bump macOS GitHub actions to macOS 11

[Kevin Rushforth]

Clean backport to jfx17u.

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Commit messages:
 - 8290527: Bump macOS GitHub actions to macOS 11

Changes: https://git.openjdk.org/jfx17u/pull/87/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx17u&pr=87&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290527
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx17u/pull/87.diff
  Fetch: git fetch https://git.openjdk.org/jfx17u pull/87/head:pull/87

PR: https://git.openjdk.org/jfx17u/pull/87