Cleanup more code related to ws2_32.dll loading in src/port/getaddrinfo.c

e2e02191 has removed a code path for Windows 2000 that attempts to load
wship6.dll as fallback if ws2_32.dll is found but not getaddrinfo(),
leaving behind a dangling pointer as the library is freed.  However,
there is no point in this check as ws2_32.dll exists since Windows XP,
so just remove the duplicated check.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/9781.1582146114@sss.pgh.pa.us

src/port/getaddrinfo.c

@@ -74,16 +74,6 @@ haveNativeWindowsIPv6routines(void)
 	 */
 	hLibrary = LoadLibraryA("ws2_32");
 
-	if (hLibrary == NULL || GetProcAddress(hLibrary, "getaddrinfo") == NULL)
-	{
-		/*
-		 * Well, ws2_32 doesn't exist, or more likely doesn't have
-		 * getaddrinfo.
-		 */
-		if (hLibrary != NULL)
-			FreeLibrary(hLibrary);
-	}
-
 	/* If hLibrary is null, we couldn't find a dll with functions */
 	if (hLibrary != NULL)
 	{