Remove reference to removed pyarrow.HdfsFile

[ritsth]

Rationale for this change

The Python memory/IO docs list pyarrow.HdfsFile as a NativeFile subclass, but that class no longer exists (legacy HDFS was deprecated in 2.0 and later removed). The :class: reference has no target, and HDFS access now uses pyarrow.fs.HadoopFileSystem, which returns regular NativeFile objects. It's the only unresolved pyarrow cross-reference on the page.

What changes are included in this PR?

Removes the stale pyarrow.HdfsFile bullet in docs/source/python/memory.rst. One line, docs only.

Are these changes tested?

Confirmed pyarrow.HdfsFile isn't in pyarrow, the ref appears only once, and all remaining :class: refs on the page resolve after removal.

Are there any user-facing changes?

Documentation only.

[github-actions]

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See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview