Fix Catastophic Backtracking for Indirect Reference (#509)

* Update regex to avoid catastrophic backtracking

* Keep regex the same. Only run heuristic for lines that are less than 1k char since that better suits the intention of the heuristic

detect_secrets/filters/heuristic.py

@@ -165,6 +165,8 @@ def is_indirect_reference(line: str) -> bool:
 
         secret = request.headers['apikey']
     """
+    if len(line) > 1000:
+        return False
     return bool(_get_indirect_reference_regex().search(line))