RFR: JDK-8254239: G1ConcurrentMark.hpp unnecessarily disables MSVC++ warning 4522

[Andrey Vershinin]

This is a simple change removing disabling of MSVC++ warning 4522. Since it only affects build process, no tests were ran.

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Commit messages:
 - 8254239: G1ConcurrentMark.hpp unnecessarily disables MSVC++ warning 4522

Changes: https://git.openjdk.java.net/jdk/pull/2646/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2646&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254239
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2646.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2646/head:pull/2646

PR: https://git.openjdk.java.net/jdk/pull/2646