fix(docs): replace yxx mappings with g== #31947

Problem:
`yx` uses "y" prefix, which shadows a builtin operator.

Solution:
Use `g=` (in the form of `g==` currently), drawing from precedent of
CTRL-= and 'tpope/vim-scriptease'.

runtime/lua/vim/treesitter/query.lua

@@ -301,7 +301,7 @@ api.nvim_create_autocmd('OptionSet', {
 ---   - `captures`: a list of unique capture names defined in the query (alias: `info.captures`).
 ---   - `info.patterns`: information about predicates.
 ---
---- Example (to try it, use `yxx` or select the code then run `:'<,'>lua`):
+--- Example (to try it, use `g==` or select the code then run `:'<,'>lua`):
 --- ```lua
 --- local query = vim.treesitter.query.parse('vimdoc', [[
 ---   ; query