RFR: 8300124: Remove unnecessary assert in GenCollectedHeap::initialize

[Albert Mingkun Yang]

Simple change of removing a redundant assertion.

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Commit messages:
 - remove-word-assert

Changes: https://git.openjdk.org/jdk/pull/11993/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11993&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300124
  Stats: 7 lines in 1 file changed: 0 ins; 7 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11993.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11993/head:pull/11993

PR: https://git.openjdk.org/jdk/pull/11993