Remove Git upgrade step from CI (#4541)

buster-backports no longer exists in debian/dists and it's breaking CI.
The currently available version of Git in this container is 2.20.1, so
we don't need this.

.github/workflows/ci.yml

@@ -69,15 +69,6 @@ jobs:
       version: "${{ steps.build.outputs.version }}"
 
     steps:
-      - # We need a proper Git repository, but the checkout step will unpack a tarball instead of doing a clone
-        # if the Git version is less than 2.18.
-        name: "(Linux only) Install a newer version of Git"
-        if: "contains(matrix.os, 'ubuntu-latest')"
-        run: |
-          . /etc/os-release
-          echo deb http://deb.debian.org/debian "$VERSION_CODENAME"-backports main >> /etc/apt/sources.list
-          apt-get update && apt-get install -y git/"$VERSION_CODENAME"-backports
-
       - # We need `gh` installed on the Linux version. Otherwise, release artifacts won't be uploaded.
         name: "(Linux only) Install gh"
         if: "contains(matrix.os, 'ubuntu-latest')"
@@ -234,13 +225,6 @@ jobs:
     container: haskell:9.2.8@sha256:b3b2f3909c7381bb96b8f18766f9407a3d6f61e0f07ea95e812583ac4f442cbb
 
     steps:
-      - # We need a proper Git repository, but the checkout step will unpack a tarball instead of doing a clone
-        # if the Git version is less than 2.18.
-        name: "Install a newer version of Git"
-        run: |
-          . /etc/os-release
-          echo deb http://deb.debian.org/debian "$VERSION_CODENAME"-backports main >> /etc/apt/sources.list
-          apt-get update && apt-get install -y git/"$VERSION_CODENAME"-backports
       - uses: "actions/checkout@v2"
 
       - name: "Fix working directory ownership"

CHANGELOG.d/internal_remove-git-upgrade-step-in-ci.md

@@ -0,0 +1 @@
+* Remove the step that upgraded Git from the CI workflow