bpo-42864: Fix compiler warning in the tokenizer with the new paren stack for column numbers (GH-24266)

diff --git a/Parser/tokenizer.c b/Parser/tokenizer.c
index f9c8bf6..d3e846c 100644
--- a/Parser/tokenizer.c
+++ b/Parser/tokenizer.c
@@ -1820,7 +1820,7 @@ tok_get(struct tok_state *tok, const char **p_start, const char **p_end)
         }
         tok->parenstack[tok->level] = c;
         tok->parenlinenostack[tok->level] = tok->lineno;
-        tok->parencolstack[tok->level] = tok->start - tok->line_start;
+        tok->parencolstack[tok->level] = (int)(tok->start - tok->line_start);
         tok->level++;
         break;
     case ')':