RFR: 8263998: Remove mentions of mc region in comments

[Yumin Qi]

Hi, Please review the simple changes for removing the mc/MC mentioned in comments.  "mc" region was removed in fix of
 https://bugs.openjdk.java.net/browse/JDK-8263002

Tests: local build.

Thanks
Yumin

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Commit messages:
 - 8263998: Remove mentions of mc region in comments

Changes: https://git.openjdk.java.net/jdk/pull/3799/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3799&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263998
  Stats: 8 lines in 3 files changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3799.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3799/head:pull/3799

PR: https://git.openjdk.java.net/jdk/pull/3799