patch 8.2.3962: build fails for missing error message

Problem:    Build fails for missing error message.
Solution:   Add changes in missed file.

src/regexp_bt.c

@@ -1392,7 +1392,8 @@ regatom(int *flagp)
       case Magic(')'):
 	if (one_exactly)
 	    EMSG_ONE_RET_NULL;
-	IEMSG_RET_NULL(_(e_internal));	// Supposed to be caught earlier.
+	// Supposed to be caught earlier.
+	IEMSG_RET_NULL(_(e_internal_error_in_regexp));
 	// NOTREACHED
 
       case Magic('='):

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3962,
 /**/
     3961,
 /**/