[hotfix] fix typo in MemorySegment

[leesf]

What is the purpose of the change

Fix typo in heapMemory field annotation in MemorySegment.

Brief change log

Fix typo in heapMemory field annotation in MemorySegment

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not documented)

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• ❌ 1. The [description] looks good.
• ❌ 2. There is [consensus] that the contribution should go into to Flink.
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• ❌ 4. The change fits into the overall [architecture].
• ❌ 5. Overall code [quality] is good.

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[StefanRRichter]

LGTM 👍