nvim: use modified a.vim plugin

To avoid bad leader binding in insert mode

.config/nvim/init.lua

@@ -648,7 +648,7 @@ require("lazy").setup({
 	"tpope/vim-sleuth", -- Detect tabstop and shiftwidth automatically
 	-- "gc" to comment visual regions/lines
 	{ "numToStr/Comment.nvim", opts = {} },
-	"vim-scripts/a.vim",
+	"mmaret/a.vim",
 })
 
 require("gen").prompts["Generate_Doxygen"] = {