[MINOR] Delete temp file from docs

[alamb]

Which issue does this PR close?

Closes #835

Rationale for this change

It is annoying that a file is left around after running cargo test

Prior to this PR, when you run cargo test --all the following file is present:

alamb@MacBook-Pro arrow-rs % git status
git status
On branch alamb/fix-publish
Untracked files:
  (use "git add <file>..." to include in what will be committed)
	parquet/data.parquet

nothing added to commit but untracked files present (use "git add" to track)

What changes are included in this PR?

Remove file in doc tests

Are there any user-facing changes?

No

[codecov-commenter]

Codecov Report

Merging #836 (72ff56e) into master (491e564) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #836   +/-   ##
=======================================
  Coverage   82.60%   82.60%           
=======================================
  Files         168      168           
  Lines       48040    48040           
=======================================
  Hits        39685    39685           
  Misses       8355     8355           

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[jimexist]

you can consider adding it to the gitignore or adopt tempfile pattern

[alamb]

While this is likely not the cleanest solution available I think it is simple and fixes the problem so I am going to merge it in.

If anyone else has a chance, cleaning it up to @jimexist 's suggestion (e.g. use tempfile) that would be great 🙏

[alamb]

🤔 well the test fails on https://github.com/apache/arrow-rs/pull/836/checks?check_run_id=3930315965 and rather than spending time debugging it I am going to take @jimexist 's advice and use .gitignore instead