patch 9.0.0091: duplicate error number

Problem:    Duplicate error number.
Solution:   Use unique error number.

src/errors.h

@@ -3312,5 +3312,5 @@ EXTERN char e_cmdline_window_already_open[]
 #endif
 #ifdef FEAT_PROP_POPUP
 EXTERN char e_cannot_use_negative_id_after_adding_textprop_with_text[]
-	INIT(= N_("E1291: Cannot use a negative id after adding a textprop with text"));
+	INIT(= N_("E1293: Cannot use a negative id after adding a textprop with text"));
 #endif

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    91,
 /**/
     90,
 /**/