RFR: 8261143: Code in MTLGraphicsConfig.m can use ThreadUtilities performOnMainThreadWaiting:YES block:^()

[Ajit Ghaisas]

1) Simplified code in MTLGraphicsConfig.m
2) Corrected method code spacing to 4 spaces from 2 spaces.

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Commit messages:
 - 8261143 - simplify code

Changes: https://git.openjdk.java.net/lanai/pull/181/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=181&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261143
  Stats: 28 lines in 1 file changed: 0 ins; 0 del; 28 mod
  Patch: https://git.openjdk.java.net/lanai/pull/181.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/181/head:pull/181

PR: https://git.openjdk.java.net/lanai/pull/181