Update heroku/buildpacks-ruby to v6.0.0 (#674)

## heroku/ruby

### Changed

- Gem install behavior and configuration ([#402](heroku/buildpacks-ruby#402))
  - Gem install path is now configured with `GEM_HOME` and `GEM_PATH` instead of `BUNDLE_PATH`.
  - Cleaning gems is now accomplished via running `bundle clean --force`. Previously it was accomplished by setting `BUNDLE_CLEAN=1`.
  - The `BUNDLE_DEPLOYMENT=1` environment variable is changed to `BUNDLE_FROZEN=1`.
  - The `BUNDLE_BIN` environment variable is no longer set.

Co-authored-by: heroku-linguist[bot] <136119646+heroku-linguist[bot]@users.noreply.github.com>

Author: heroku-linguist[bot]

builder-20/builder.toml

@@ -47,7 +47,7 @@ version = "0.20.6"
 
 [[buildpacks]]
   id = "heroku/ruby"
-  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:cac24ba470c16cb0a153801f2b15ffebf77995a346f404767519174061aac78d"
+  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:f5a251145bc50c2ed7add82ff37536389e8c7f5a1bc5e598f22cc3c15e862f19"
 
 [[buildpacks]]
   id = "heroku/scala"
@@ -80,7 +80,7 @@ version = "0.20.6"
     optional = true
   [[order.group]]
     id = "heroku/ruby"
-    version = "5.1.0"
+    version = "6.0.0"
   [[order.group]]
     id = "heroku/procfile"
     version = "4.1.0"

builder-22/builder.toml

@@ -51,7 +51,7 @@ version = "0.20.6"
 
 [[buildpacks]]
   id = "heroku/ruby"
-  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:cac24ba470c16cb0a153801f2b15ffebf77995a346f404767519174061aac78d"
+  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:f5a251145bc50c2ed7add82ff37536389e8c7f5a1bc5e598f22cc3c15e862f19"
 
 [[buildpacks]]
   id = "heroku/scala"
@@ -89,7 +89,7 @@ version = "0.20.6"
     optional = true
   [[order.group]]
     id = "heroku/ruby"
-    version = "5.1.0"
+    version = "6.0.0"
   [[order.group]]
     id = "heroku/procfile"
     version = "4.1.0"

builder-24/builder.toml

@@ -51,7 +51,7 @@ mirrors = ["public.ecr.aws/heroku/heroku:24"]
 
 [[buildpacks]]
   id = "heroku/ruby"
-  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:cac24ba470c16cb0a153801f2b15ffebf77995a346f404767519174061aac78d"
+  uri = "docker://docker.io/heroku/buildpack-ruby@sha256:f5a251145bc50c2ed7add82ff37536389e8c7f5a1bc5e598f22cc3c15e862f19"
 
 [[buildpacks]]
   id = "heroku/scala"
@@ -89,7 +89,7 @@ mirrors = ["public.ecr.aws/heroku/heroku:24"]
     optional = true
   [[order.group]]
     id = "heroku/ruby"
-    version = "5.1.0"
+    version = "6.0.0"
   [[order.group]]
     id = "heroku/procfile"
     version = "4.1.0"