Make GenericAlias_Type and Generic_Type static. (GH-8076)

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 41d059b..014c2f3 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -5194,7 +5194,7 @@
     {NULL}  /* sentinel */
 };
 
-PyTypeObject GenericAlias_Type = {
+static PyTypeObject GenericAlias_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "GenericAlias",
     sizeof(PyGenericAliasObject),
@@ -5231,7 +5231,7 @@
     {NULL}  /* sentinel */
 };
 
-PyTypeObject Generic_Type = {
+static PyTypeObject Generic_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "Generic",
     sizeof(PyGenericObject),