update Go to 1.21.5 (#15592)

for https://github.com/fleetdm/fleet/issues/15584

# Checklist for submitter

If some of the following don't apply, delete the relevant line.

<!-- Note that API documentation changes are now addressed by the
product design team. -->

- [x] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [x] Manual QA for all new/changed functionality

.github/workflows/deploy-fleet-website.yml

@@ -59,7 +59,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
       with:
-        go-version: 1.21
+        go-version: ${{ vars.GO_VERSION }}
 
     # Download top-level dependencies and build Storybook in the website's assets/ folder
     - run: npm install --legacy-peer-deps && npm run build-storybook -- -o ./website/assets/storybook --loglevel verbose

.github/workflows/dogfood-deploy.yml

@@ -51,7 +51,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
         with:
-          go-version: '1.21'
+          go-version: ${{ vars.GO_VERSION }}
       - uses: hashicorp/setup-terraform@633666f66e0061ca3b725c73b2ec20cd13a8fdd1 # v2.0.3
         with:
           terraform_version: 1.6.3

.github/workflows/fleetctl-preview-latest.yml

@@ -51,7 +51,7 @@ jobs:
         #   - Unattended installation of Docker on macOS fails. (see
         #   https://github.com/docker/for-mac/issues/6450)
         os: [ubuntu-latest]
-        go-version: ['1.21.1']
+        go-version: ['${{ vars.GO_VERSION }}']
     runs-on: ${{ matrix.os }}
     steps: