Revert "Use word-boundary regex to detect now in CEL expressions"

This reverts commit f6b1c39.

Author: stefanvanburen

protovalidate/internal/rules.py

@@ -14,7 +14,6 @@
 
 import dataclasses
 import datetime
-import re
 import typing
 from collections.abc import Callable, Container, Iterable, Mapping
 
@@ -45,9 +44,6 @@ def _is_repeated(field: descriptor.FieldDescriptor) -> bool:
         return field.label == descriptor.FieldDescriptor.LABEL_REPEATED  # type: ignore[attr-defined]
 
 
-_NOW_RE = re.compile(r"\bnow\b")
-
-
 class CompilationError(Exception):
     pass
 
@@ -417,7 +413,7 @@ def add_rule(
             rules = validate_pb2.Rule()
             rules.id = expression
             rules.expression = expression
-        if _NOW_RE.search(rules.expression):
+        if "now" in rules.expression:
             self._uses_now = True
         ast = env.compile(rules.expression)
         prog = env.program(ast, functions=funcs)