chore: update setup-go action to fix Go download failures (#22306)

setup-go has been sporadically failing to download Go, and we were advised
by a member of the Go team that downloading Go from `storage.googleapis.com`
is not guaranteed (which is what setup-go <= v5.6.0 does).

Also remove the use-preinstalled-go optimization for Windows runners.
setup-go v6 sets GOTOOLCHAIN=local, which prevents the pre-installed
Go from auto-downloading the toolchain specified in go.mod. The windows
optimization with v5 relied on GOTOOLCHAIN=auto. setup-go uses the runner
cache, which is a different caching path but should serve the same purpose.

.github/actions/setup-go/action.yaml

@@ -5,9 +5,6 @@ inputs:
   version:
     description: "The Go version to use."
     default: "1.25.7"
-  use-preinstalled-go:
-    description: "Whether to use preinstalled Go."
-    default: "false"
   use-cache:
     description: "Whether to use the cache."
     default: "true"
@@ -15,9 +12,9 @@ runs:
   using: "composite"
   steps:
     - name: Setup Go
-      uses: actions/setup-go@0a12ed9d6a96ab950c8f026ed9f722fe0da7ef32 # v5.0.2
+      uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5.6.0
       with:
-        go-version: ${{ inputs.use-preinstalled-go == 'false' && inputs.version || '' }}
+        go-version: ${{ inputs.version }}
         cache: ${{ inputs.use-cache }}
 
     - name: Install gotestsum

.github/workflows/ci.yaml

@@ -422,10 +422,6 @@ jobs:
       - name: Setup Go
         uses: ./.github/actions/setup-go
         with:
-          # Runners have Go baked-in and Go will automatically
-          # download the toolchain configured in go.mod, so we don't
-          # need to reinstall it. It's faster on Windows runners.
-          use-preinstalled-go: ${{ runner.os == 'Windows' }}
           use-cache: true
 
       - name: Setup Terraform

.github/workflows/nightly-gauntlet.yaml

@@ -64,11 +64,6 @@ jobs:
 
       - name: Setup Go
         uses: ./.github/actions/setup-go
-        with:
-          # Runners have Go baked-in and Go will automatically
-          # download the toolchain configured in go.mod, so we don't
-          # need to reinstall it. It's faster on Windows runners.
-          use-preinstalled-go: ${{ runner.os == 'Windows' }}
 
       - name: Setup Terraform
         uses: ./.github/actions/setup-tf