RFR: 8254285: G1: Remove "What is this about" comment in G1CollectedHeap.cpp

[Thomas Schatzl]

Hi all,

  can I get quick reviews for this imho trivial change that removes some strange comment leftover from initial G1 import
  reading:

   // FIXME: what is this about?
  // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
  // is set.

None of the referenced identifiers are in any kind of recent code base (looking back to some pre-g1 7u changes). In its
current context it does not make sense either and apparently whatever omission the comment suggests has not hurt G1 for
years.

Testing: local compilation

Thanks,
  Thomas

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Commit messages:
 - Initial import

Changes: https://git.openjdk.java.net/jdk/pull/573/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=573&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254285
  Stats: 3 lines in 1 file changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/573.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/573/head:pull/573

PR: https://git.openjdk.java.net/jdk/pull/573