Build(deps): Bump rack-proxy from 0.7.6 to 0.7.7 in /Builder

Bumps [rack-proxy](https://github.com/ncr/rack-proxy) from 0.7.6 to 0.7.7.
- [Commits](ncr/rack-proxy@v0.7.6...v0.7.7)

---
updated-dependencies:
- dependency-name: rack-proxy
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Builder/Gemfile.lock

@@ -164,7 +164,7 @@ GEM
       rack (>= 1, < 4)
     rack-cors (2.0.1)
       rack (>= 2.0.0)
-    rack-proxy (0.7.6)
+    rack-proxy (0.7.7)
       rack
     rack-test (2.1.0)
       rack (>= 1.3)