Switch $\Z to \Z in matching regex

This was the aim of d761d0e but a
typo included both. \Z is a stricter form of $.

src/werkzeug/routing/rules.py

@@ -626,7 +626,7 @@ def _parse_rule(self, rule: str) -> t.Iterable[RulePart]:
                     argument_weights,
                 )
                 if not static:
-                    content += r"$\Z"
+                    content += r"\Z"
                 yield RulePart(
                     content=content, final=final, static=static, weight=weight
                 )