Simplify static function in extension.c

An extra argument for the filename defining the extension script
location was present, aimed at being used for error reporting, but has
never been used.  This was around since extensions have been added in
d9572c4e.

Author: Yugo Nagata
Reviewed-by: Tatsuo Ishii
Discussion: https://postgr.es/m/20180907180504.1ff19e1675bb44a67e9c7ab1@sraoss.co.jp

src/backend/commands/extension.c

@@ -683,8 +683,6 @@ read_extension_script_file(const ExtensionControlFile *control,
 /*
  * Execute given SQL string.
  *
- * filename is used only to report errors.
- *
  * Note: it's tempting to just use SPI to execute the string, but that does
  * not work very well.  The really serious problem is that SPI will parse,
  * analyze, and plan the whole string before executing any of it; of course
@@ -694,7 +692,7 @@ read_extension_script_file(const ExtensionControlFile *control,
  * could be very long.
  */
 static void
-execute_sql_string(const char *sql, const char *filename)
+execute_sql_string(const char *sql)
 {
 	List	   *raw_parsetree_list;
 	DestReceiver *dest;
@@ -921,7 +919,7 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 		/* And now back to C string */
 		c_sql = text_to_cstring(DatumGetTextPP(t_sql));
 
-		execute_sql_string(c_sql, filename);
+		execute_sql_string(c_sql);
 	}
 	PG_CATCH();
 	{