Update heroku/buildpacks-python to v2.7.3 (#839)

## heroku/python

### Changed

- The Python 3.9 version alias now resolves to Python 3.9.25. ([#458](heroku/buildpacks-python#458))
- Updated uv from 0.9.5 to 0.9.7. ([#455](heroku/buildpacks-python#455))

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

Author: heroku-linguist[bot]

builder-22/builder.toml

@@ -47,7 +47,7 @@ version = "0.20.16"
 
 [[buildpacks]]
   id = "heroku/python"
-  uri = "docker://docker.io/heroku/buildpack-python@sha256:495a0c3f393b49429383477561de9d7c77c42dffaef0143b244c9beb075552aa"
+  uri = "docker://docker.io/heroku/buildpack-python@sha256:e54dba0cc03c21a5d983e3732f6a07ec1fcba20b680b93d877ef23a9c1967f89"
 
 [[buildpacks]]
   id = "heroku/ruby"
@@ -64,7 +64,7 @@ version = "0.20.16"
     optional = true
   [[order.group]]
     id = "heroku/python"
-    version = "2.7.2"
+    version = "2.7.3"
   [[order.group]]
     id = "heroku/procfile"
     version = "4.2.1"

builder-24/builder.toml

@@ -47,7 +47,7 @@ mirrors = ["public.ecr.aws/heroku/heroku:24"]
 
 [[buildpacks]]
   id = "heroku/python"
-  uri = "docker://docker.io/heroku/buildpack-python@sha256:495a0c3f393b49429383477561de9d7c77c42dffaef0143b244c9beb075552aa"
+  uri = "docker://docker.io/heroku/buildpack-python@sha256:e54dba0cc03c21a5d983e3732f6a07ec1fcba20b680b93d877ef23a9c1967f89"
 
 [[buildpacks]]
   id = "heroku/ruby"
@@ -64,7 +64,7 @@ mirrors = ["public.ecr.aws/heroku/heroku:24"]
     optional = true
   [[order.group]]
     id = "heroku/python"
-    version = "2.7.2"
+    version = "2.7.3"
   [[order.group]]
     id = "heroku/procfile"
     version = "4.2.1"