Issue #18722: Remove uses of the "register" keyword in C code.
diff --git a/Objects/unicodectype.c b/Objects/unicodectype.c
index a572c12..ea540d6 100644
--- a/Objects/unicodectype.c
+++ b/Objects/unicodectype.c
@@ -61,7 +61,7 @@
 /* Returns the titlecase Unicode characters corresponding to ch or just
    ch if no titlecase mapping is known. */
 
-Py_UCS4 _PyUnicode_ToTitlecase(register Py_UCS4 ch)
+Py_UCS4 _PyUnicode_ToTitlecase(Py_UCS4 ch)
 {
     const _PyUnicode_TypeRecord *ctype = gettyperecord(ch);