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MINOR: [R][Docs] Minor documentation fixes (#34337)

### Rationale for this change

Make small improvements that I noticed while reading the documentation.

### What changes are included in this PR?

- Fix typo of inline code (``` `format = "parquet"`` ``` to `` `format = "parquet"` ``)
- Link `FileFormat$create()` to `FileFormat`
- Updating Rd file I forgot to update in #33968

### Are these changes tested?

Only the documentation is changed, and the generated Rd files are included in this PR.

### Are there any user-facing changes?

No.

Authored-by: SHIMA Tatsuya <ts1s1andn@gmail.com>
Signed-off-by: Dewey Dunnington <dewey@fishandwhistle.net>