Escape single quotes in docstring

[syohex]

Emacs 29 or higher veresions warn unescaped single quotes in docstrings.

In go-guru-implements:
go-guru.el:398:2: Warning: docstring has wrong usage of unescaped single
    quotes (use \=' or different quoting such as `...')

go-mode.el:149:2: Warning: custom-declare-variable `go-command' docstring has
    wrong usage of unescaped single quotes (use \=' or different quoting such
    as `...')
go-mode.el:158:2: Warning: custom-declare-variable `gofmt-command' docstring
    has wrong usage of unescaped single quotes (use \=' or different quoting
    such as `...')
go-mode.el:183:2: Warning: custom-declare-variable `godef-command' docstring
    has wrong usage of unescaped single quotes (use \=' or different quoting
    such as `...')
go-mode.el:195:2: Warning: custom-declare-variable `go-packages-function'
    docstring has wrong usage of unescaped single quotes (use \=' or different
    quoting such as `...')

...