Merge pull request #69002 from akien-mga/gdscript-disable-warning-RETURN_VALUE_DISCARDED

GDScript: Don't warn about RETURN_VALUE_DISCARDED by default

doc/classes/ProjectSettings.xml

@@ -401,7 +401,7 @@
 		<member name="debug/gdscript/warnings/redundant_await" type="int" setter="" getter="" default="1">
 			When set to [code]warn[/code] or [code]error[/code], produces a warning or an error respectively when a function that is not a coroutine is called with await.
 		</member>
-		<member name="debug/gdscript/warnings/return_value_discarded" type="int" setter="" getter="" default="1">
+		<member name="debug/gdscript/warnings/return_value_discarded" type="int" setter="" getter="" default="0">
 			When set to [code]warn[/code] or [code]error[/code], produces a warning or an error respectively when calling a function without using its return value (by assigning it to a variable or using it as a function argument). Such return values are sometimes used to denote possible errors using the [enum Error] enum.
 		</member>
 		<member name="debug/gdscript/warnings/shadowed_global_identifier" type="int" setter="" getter="" default="1">

modules/gdscript/gdscript_warning.cpp

@@ -171,6 +171,10 @@ int GDScriptWarning::get_default_value(Code p_code) {
 	if (get_name_from_code(p_code).to_lower().begins_with("unsafe_")) {
 		return WarnLevel::IGNORE;
 	}
+	// Too spammy by default on common cases (connect, Tween, etc.).
+	if (p_code == RETURN_VALUE_DISCARDED) {
+		return WarnLevel::IGNORE;
+	}
 	return WarnLevel::WARN;
 }