RFR: 8318100: Remove redundant check for Metal support

[Jayathirth D V]

We have updated minimum macOS version on which JDK can be used to macOS 11 and we have check to enable metal pipeline only when macOS version is >=10.14.

Since minimum macOS version is updated we don't need this check now.
Removed redundant check and ran all clientlibs tests on CI for verification.
Also ran a sample program with different combination of sun.java2d.metal and sun.java2d.opengl flags and i see that appropriate pipeline is getting selected.

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Commit messages:
 - 8318100: Remove redundant check for Metal support

Changes: https://git.openjdk.org/jdk/pull/16316/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16316&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318100
  Stats: 40 lines in 3 files changed: 0 ins; 39 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16316.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16316/head:pull/16316

PR: https://git.openjdk.org/jdk/pull/16316