comctl32: Remove redundant function declaration

[Andrew Talbot]

Changelog:
    comctl32: Remove redundant function declaration. MONTHCAL_CopyTime(), in
comctl32/monthcal.c, is now static.

diff --git a/dlls/comctl32/datetime.c b/dlls/comctl32/datetime.c
index abfef58..785769a 100644
--- a/dlls/comctl32/datetime.c
+++ b/dlls/comctl32/datetime.c
@@ -135,7 +135,6 @@ extern int MONTHCAL_CalculateDayOfWeek(SYSTEMTIME *date, BOOL inplace);
 
 static BOOL DATETIME_SendSimpleNotify (const DATETIME_INFO *infoPtr, UINT code);
 static BOOL DATETIME_SendDateTimeChangeNotify (const DATETIME_INFO *infoPtr);
-extern void MONTHCAL_CopyTime(const SYSTEMTIME *from, SYSTEMTIME *to);
 static const WCHAR allowedformatchars[] = {'d', 'h', 'H', 'm', 'M', 's', 't', 'y', 'X', 0};
 static const int maxrepetition [] = {4,2,2,2,4,2,2,4,-1};