RFR: 8337997: MallocHeader description refers to non-existent NMT state "minimal"

[Casper Norrbin]

Hi everyone,

Small fix to a comment in `mallocHeader.hpp`, which referenced a non-existant NMT state. This has been changed to the correct (existing) state.

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Commit messages:
 - fix mallocheader comment

Changes: https://git.openjdk.org/jdk/pull/23199/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23199&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337997
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23199.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23199/head:pull/23199

PR: https://git.openjdk.org/jdk/pull/23199