Make GenericAlias_Type and Generic_Type static. (GH-8076)

(cherry picked from commit 97ae32c9)
Co-authored-by: Benjamin Peterson <benjamin@python.org>

Modules/_testcapimodule.c

@@ -5200,7 +5200,7 @@ static PyMethodDef generic_alias_methods[] = {
     {NULL}  /* sentinel */
 };
 
-PyTypeObject GenericAlias_Type = {
+static PyTypeObject GenericAlias_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "GenericAlias",
     sizeof(PyGenericAliasObject),
@@ -5237,7 +5237,7 @@ static PyMethodDef generic_methods[] = {
     {NULL}  /* sentinel */
 };
 
-PyTypeObject Generic_Type = {
+static PyTypeObject Generic_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "Generic",
     sizeof(PyGenericObject),