MDEV-4573 UNINSTALL PLUGIN misleading error message for non-dynamic plugins

change WARN_PLUGIN_DELETE_BUILTIN to ER_PLUGIN_DELETE_BUILTIN

include/mysql.h

@@ -135,6 +135,7 @@ typedef unsigned long long my_ulonglong;
 
 /* backward compatibility define - to be removed eventually */
 #define ER_WARN_DATA_TRUNCATED WARN_DATA_TRUNCATED
+#define WARN_PLUGIN_DELETE_BUILTIN ER_PLUGIN_DELETE_BUILTIN
 
 typedef struct st_mysql_rows {
   struct st_mysql_rows *next;		/* list of rows */

mysql-test/r/plugin.result

@@ -171,3 +171,5 @@ select 1;
 1
 1
 UNINSTALL PLUGIN example;
+UNINSTALL PLUGIN MyISAM;
+ERROR HY000: Built-in plugins cannot be deleted

mysql-test/t/plugin.test

@@ -148,3 +148,10 @@ SET @@SQL_MODE=@OLD_SQL_MODE;
 #
 select 1;
 UNINSTALL PLUGIN example;
+
+#
+# MDEV-4573 UNINSTALL PLUGIN misleading error message for non-dynamic plugins
+#
+--error ER_PLUGIN_DELETE_BUILTIN
+UNINSTALL PLUGIN MyISAM;
+

sql/share/errmsg-utf8.txt

@@ -6161,7 +6161,7 @@ WARN_NO_MASTER_INFO
 WARN_OPTION_IGNORED
   eng "<%-.64s> option ignored"
   ger "Option <%-.64s> ignoriert"
-WARN_PLUGIN_DELETE_BUILTIN
+ER_PLUGIN_DELETE_BUILTIN
   eng "Built-in plugins cannot be deleted"
   ger "Eingebaute Plugins können nicht gelöscht werden"
 WARN_PLUGIN_BUSY

sql/sql_plugin.cc

@@ -2174,9 +2174,7 @@ static bool do_uninstall(THD *thd, TABLE *table, const LEX_STRING *name)
   }
   if (!plugin->plugin_dl)
   {
-    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
-                 WARN_PLUGIN_DELETE_BUILTIN, ER(WARN_PLUGIN_DELETE_BUILTIN));
-    my_error(ER_SP_DOES_NOT_EXIST, MYF(0), "PLUGIN", name->str);
+    my_error(ER_PLUGIN_DELETE_BUILTIN, MYF(0));
     return 1;
   }
   if (plugin->load_option == PLUGIN_FORCE_PLUS_PERMANENT)