test(catalog_spark): bound weed shell invocation with 30s timeout

createTableBucket ran `weed shell` via exec.Command with no deadline.
When the shell's first command retries on a transient master connection
blip, the trailing `exit` on stdin never gets processed and the
subprocess blocks until the outer 20m `go test` timeout fires — the
surfacing symptom is a flaky 20m panic with no diagnostic output.

Wrap the invocation in exec.CommandContext with a 30s timeout, matching
the existing pattern in test/s3tables/catalog_risingwave/setup_test.go.

test/s3tables/catalog_spark/setup_test.go

@@ -323,8 +323,11 @@ spark = (SparkSession.builder
 func createTableBucket(t *testing.T, env *TestEnvironment, bucketName string) {
 	t.Helper()
 
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
 	masterGrpcPort := env.masterPort + 10000
-	cmd := exec.Command("weed", "shell",
+	cmd := exec.CommandContext(ctx, "weed", "shell",
 		fmt.Sprintf("-master=localhost:%d.%d", env.masterPort, masterGrpcPort),
 	)
 	cmd.Stdin = strings.NewReader(fmt.Sprintf("s3tables.bucket -create -name %s -account 000000000000\nexit\n", bucketName))