Fix typos in source code using codespell

From https://github.com/lucasdemarchi/codespell

modules/visual_script/visual_script_expression.cpp

@@ -1180,7 +1180,7 @@ VisualScriptExpression::ENode *VisualScriptExpression::_parse_expression() {
 				// this is not invalid and can really appear
 				// but it becomes invalid anyway because no binary op
 				// can be followed by an unary op in a valid combination,
-				// due to how precedence works, unaries will always dissapear first
+				// due to how precedence works, unaries will always disappear first
 
 				_set_error("Unexpected two consecutive operators.");
 				return NULL;