proxy: v2.168.0 (#7352)

This release includes no user-facing changes.

The proxy's outbound HTTP router has been refactored to support upcoming
changes.

---

* build(deps): bump serde_json from 1.0.70 to 1.0.71 (linkerd/linkerd2-proxy#1383)
* ci: Run dependabot updates at 2AM PST (linkerd/linkerd2-proxy#1384)
* build(deps): bump tower from 0.4.10 to 0.4.11 (linkerd/linkerd2-proxy#1385)
* ci: Fix coverage workflow (linkerd/linkerd2-proxy#1382)
* outbound: Use per-route services in routing stack (linkerd/linkerd2-proxy#1380)
* build(deps): bump tracing-subscriber from 0.3.1 to 0.3.2 (linkerd/linkerd2-proxy#1387)
* build(deps): bump libc from 0.2.107 to 0.2.108 (linkerd/linkerd2-proxy#1386)
* build(deps): bump futures from 0.3.17 to 0.3.18 (linkerd/linkerd2-proxy#1388)

.proxy-version

@@ -1 +1 @@
-v2.167.0
+v2.168.0