build(deps): bump rack-session in /appengine/flexible/hello_world (#1575)

Bumps [rack-session](https://github.com/rack/rack-session) from 2.1.0 to 2.1.1.
- [Release notes](https://github.com/rack/rack-session/releases)
- [Changelog](https://github.com/rack/rack-session/blob/main/releases.md)
- [Commits](rack/rack-session@v2.1.0...v2.1.1)

---
updated-dependencies:
- dependency-name: rack-session
  dependency-version: 2.1.1
  dependency-type: indirect
...

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Author: dependabot[bot]

appengine/flexible/hello_world/Gemfile.lock

@@ -1,20 +1,20 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    base64 (0.2.0)
+    base64 (0.3.0)
     diff-lcs (1.6.1)
     logger (1.7.0)
     mustermann (3.0.3)
       ruby2_keywords (~> 0.0.1)
     nio4r (2.7.4)
     puma (6.6.0)
       nio4r (~> 2.0)
-    rack (3.1.13)
+    rack (3.1.16)
     rack-protection (4.1.1)
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-session (2.1.0)
+    rack-session (2.1.1)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
     rack-test (2.2.0)
@@ -50,7 +50,6 @@ GEM
 PLATFORMS
   ruby
 
-
 DEPENDENCIES
   puma (~> 6.6)
   rack-test