Fixed Style/StringLiterals RuboCop offense

Fixed Style/StringLiterals RuboCop offense

$ bundle exec rubocop --auto-correct
Inspecting 25 files
CC....C.......CCCCCCCCC.C

Offenses:

Gemfile:4:8: C: [Corrected] Prefer single-quoted strings when you don't
need string interpolation or special symbols.
source "https://rubygems.org"
^^^^^^^^^^^^^^^^^^^^^^
…
25 files inspected, 81 offenses detected, 81 offenses corrected

Bug: T91485
Change-Id: Ic6f1337fa465e8c90e5aa7ea3540eb6bfad15af8