fix: skip pre-releases when selecting Coder versions for integration tests

The coderversion script was including release candidates when scanning
GitHub releases, then stripping the pre-release suffix to form the
version string (e.g. v2.32.0-rc.0 → v2.32.0). This caused integration
tests to pull a Docker image that doesn't exist yet, failing with
"manifest unknown".

Author: matifali

scripts/coderversion/main.go

@@ -99,7 +99,8 @@ func main() {
 }
 
 type release struct {
-	TagName string `json:"tag_name"`
+	TagName    string `json:"tag_name"`
+	Prerelease bool   `json:"prerelease"`
 }
 
 const releasesURL = "https://api.github.com/repos/coder/coder/releases"
@@ -121,9 +122,8 @@ func fetchReleases() []string {
 
 	var ss []string
 	for _, rel := range releases {
-		if rel.TagName != "" {
+		if rel.TagName != "" && !rel.Prerelease {
 			ss = append(ss, rel.TagName)
-
 		}
 	}
 	return ss