Remove "Modifier" from RestoreDefaultKeyboardModifierRemappings

- Remove "Modifier" from the method name since it'll also be
  responsible for resetting the six pack key remappings.

Context: https://crrev.com/c/4585862/comment/15629039_1d45f79a/

Change-Id: I03ecd63a09a19e8f0e3168c2206eaa618bfc3039
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4619527
Reviewed-by: David Padlipsky <dpad@google.com>
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Commit-Queue: Michael Checo <michaelcheco@google.com>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1159171}