Remove 503, 504 retries from corso retry handler (#3435)

Remove overlap between corso retry handler & kiota retry handler. 
Since kiota retry handler supports [503, 504 retries](fb98fba2da/retry_handler.go (L170)), we don't need to duplicate these retries in corso retry handler.

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #<issue>

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/connector/graph/middleware.go

@@ -343,9 +343,7 @@ func (mw RetryMiddleware) retryRequest(
 
 var retryableRespCodes = []int{
 	http.StatusInternalServerError,
-	http.StatusServiceUnavailable,
 	http.StatusBadGateway,
-	http.StatusGatewayTimeout,
 }
 
 func (mw RetryMiddleware) isRetriableRespCode(ctx context.Context, resp *http.Response, code int) bool {