build(deps): bump oauth2-proxy/oauth2-proxy in /oauth2-proxy

Bumps [oauth2-proxy/oauth2-proxy](https://github.com/oauth2-proxy/oauth2-proxy) from v7.14.3-alpine to v7.15.0-alpine.
- [Release notes](https://github.com/oauth2-proxy/oauth2-proxy/releases)
- [Changelog](https://github.com/oauth2-proxy/oauth2-proxy/blob/master/CHANGELOG.md)
- [Commits](oauth2-proxy/oauth2-proxy@v7.14.3...v7.15.0)

---
updated-dependencies:
- dependency-name: oauth2-proxy/oauth2-proxy
  dependency-version: v7.15.0-alpine
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

oauth2-proxy/Dockerfile

@@ -1,4 +1,4 @@
-FROM quay.io/oauth2-proxy/oauth2-proxy:v7.14.3-alpine AS oauth2-proxy
+FROM quay.io/oauth2-proxy/oauth2-proxy:v7.15.0-alpine AS oauth2-proxy
 
 ENV TZ=Europe/Berlin