RFR: 8298568: Fastdebug build fails after JDK-8296389

[Fei Yang]

This is a trivial change fixing an typo introduced by JDK-8296389.
The correct version is "is_NeverBranch()" instead of "isNeverBranch()".

Testing: Fastdebug builds fine with this fix on linux-aarch64 platform.

-------------

Commit messages:
 - 8298568: Fastdebug build fails after JDK-8296389

Changes: https://git.openjdk.org/jdk/pull/11631/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11631&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298568
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11631.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11631/head:pull/11631

PR: https://git.openjdk.org/jdk/pull/11631