Settings: Increase char limit of show refresh rate

Increase the char limit for the developer option "show refresh rate"
to accommodate translations.

Bug: 146766957
Bug: 146766391
Change-Id: I324356278a31551db6da74ef0eb09068d36122b2
Test: Set a 36 char string on "show_refresh_rate" and observe no truncation
Test: Set a 58 char string on "show_refresh_rate_summary" and observe no truncation