Fix start_tag leak in the vendored SQL scanner deserialize

tree_sitter_sql_external_scanner_deserialize set state->start_tag = NULL and re-malloc'd it without freeing the previous allocation. tree-sitter calls deserialize repeatedly during a parse, leaking the prior start_tag each time (LeakSanitizer, Linux x64). Free it first — safe since create() NULL-inits it and destroy() frees+NULLs it.

internal/cbm/vendored/grammars/sql/scanner.c

@@ -179,6 +179,7 @@ unsigned tree_sitter_sql_external_scanner_serialize(void *payload, char *buffer)
 
 void tree_sitter_sql_external_scanner_deserialize(void *payload, const char *buffer, unsigned length) {
   LexerState *state = (LexerState *)payload;
+  free(state->start_tag); /* deserialize is called repeatedly; free the prior tag first */
   state->start_tag = NULL;
   // A length of 1 can't exists.
   if (length > 1) {