Improve GDScript autocompletion for methods

modules/gdscript/tests/scripts/completion/common/identifiers_in_call.cfg

@@ -2,13 +2,13 @@ scene="res://completion/get_node/get_node.tscn"
 [output]
 include=[
     ; Node
-    {"display": "add_child"},
+    {"display": "add_child(…)"},
     {"display": "owner"},
     {"display": "child_entered_tree"},
 
     ; GDScript: class_a.notest.gd
     {"display": "property_of_a"},
-    {"display": "func_of_a"},
+    {"display": "func_of_a()"},
     {"display": "signal_of_a"},
 
     ; GDScript: identifiers.gd
@@ -16,8 +16,8 @@ include=[
     {"display": "test_signal_2"},
     {"display": "test_var_1"},
     {"display": "test_var_2"},
-    {"display": "test_func_1"},
-    {"display": "test_func_2"},
+    {"display": "test_func_1(…)"},
+    {"display": "test_func_2(…)"},
     {"display": "test_parameter_1"},
     {"display": "test_parameter_2"},
     {"display": "local_test_var_1"},