Update git submodules
- Update extensions/SyntaxHighlight_GeSHi from branch 'REL1_31' to 12fbfd414c02116376b68fbd43f16563eae6ca19
- Update README to match pygments version
Bug: T235808 Change-Id: Iea9a1bc566f67507414f7f2a4fdfd89c8433b7fd Follows-Up: I4dc1782f19881ba1294308e1cdea1b2e063f438a (cherry picked from commit e286f3be4fada723e8a4cd32db2e56d32397f8d3)
- Update README to match pygments version