Beautify ada_mode to conform to lua standards

lua/ada_mode.lua

@@ -1,8 +1,3 @@
--- Lua vim-dummy variable
-if vim == nil then
-	local vim = {}
-end
-
 -- @name Prove
 -- @param
 -- @short Run gnatprove
@@ -12,7 +7,7 @@ function Prove()
 	vim.api.nvim_buf_set_lines(0, 0, -1, false, run_cmd)
 	vim.cmd(":%!bash")
 
-	buffer_loaded = true
+	Buffer_loaded = true
 end
 
 -- @name Run
@@ -24,12 +19,12 @@ function Run()
 	vim.api.nvim_buf_set_lines(0, 0, -1, false, run_cmd)
 	vim.cmd(":%!bash")
 
-	buffer_loaded = true
+	Buffer_loaded = true
 end
 
 function Close_Prove()
-	if buffer_loaded then
-		buffer_loaded = false
+	if Buffer_loaded then
+		Buffer_loaded = false
 		vim.cmd("bd!")
 	end
 end