workflows: use symbolic name oldstable instead of a particular version

The actions/setup-go action has supported symbolic names of `stable` and
`oldstable` for a bit. Instead of having to constantly update the
workflow every time Go does a new release use the `oldstable` keyword in
our workflow so that we're always testing with the older stable release
of Go. We choose the older stable version because we do not want to
accidentally introduce something new that requires a feature of the
newer Go release.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

.github/workflows/main.yml

@@ -13,7 +13,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.19"
+          go-version: oldstable
       - uses: actions/checkout@v3
       - name: Build
         run: make
@@ -23,7 +23,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.19"
+          go-version: oldstable
       - uses: actions/checkout@v3
       - name: Install revive
         run: go install github.com/mgechev/revive@latest
@@ -46,7 +46,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.19"
+          go-version: oldstable
       - uses: actions/checkout@v3
       - name: run the tests
         run: make test
@@ -100,7 +100,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v3
         with:
-          go-version: "1.19"
+          go-version: oldstable
       - name: Install k3d
         run: curl -L --silent --fail "https://raw.githubusercontent.com/rancher/k3d/main/install.sh" | bash
       # The TAG env var can interfere with the k3d install script.