test: fix few e2e flaky tests (#7762)

**Motivation**

Make our tests more stable on CI. 

**Description**

Fix following flaky tests 

- `packages/beacon-node/test/e2e/network/reqresp.test.ts` 
- [AxiosError: Request failed with status code
429](https://github.com/ChainSafe/lodestar/actions/runs/14731164867/job/41349996153?pr=7762#step:6:10755)


Partially Closes #6358

**Steps to test or reproduce**

- Run all tests on CI

packages/params/test/e2e/ensure-config-is-synced.test.ts

@@ -52,14 +52,19 @@ function assertCorrectPreset(localPreset: BeaconPreset, remotePreset: BeaconPres
 }
 
 async function downloadRemoteConfig(preset: "mainnet" | "minimal", commit: string): Promise<BeaconPreset> {
-  const downloadedParams = await Promise.all(
-    Object.values(ForkName).map((forkName) =>
-      axios({
-        url: `https://raw.githubusercontent.com/ethereum/consensus-specs/${commit}/presets/${preset}/${forkName}.yaml`,
-        timeout: 30 * 1000,
-      }).then((response) => loadConfigYaml(response.data))
-    )
-  );
+  const downloadedParams: Record<string, unknown>[] = [];
+
+  for (const forkName of Object.values(ForkName)) {
+    const response = await axios({
+      url: `https://raw.githubusercontent.com/ethereum/consensus-specs/${commit}/presets/${preset}/${forkName}.yaml`,
+      timeout: 30 * 1000,
+    });
+    downloadedParams.push(loadConfigYaml(response.data));
+
+    // We get error `Request failed with status code 429`
+    // which is `Too Many Request` so we added a bit delay between each request
+    await new Promise((resolve) => setTimeout(resolve, 200));
+  }
 
   // Merge all the fetched yamls for the different forks
   const beaconPresetRaw: Record<string, unknown> = Object.assign(