Revert "Add default rustfmt.toml"

This reverts commit f57514ff.

This change broke rustfmt being invoked directly.

Could not parse TOML: expected a table key, found a period at line
1 column 1

Test: Ran rustfmt, cargo-fmt and repo upload
Change-Id: I6caa143c49b88634ef04c7d1f822572737128521