Use status code constant (#864)

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## What type of PR is this? (check all applicable)

- [x] Refactor
- [ ] Feature
- [ ] Bug Fix
- [ ] Optimization
- [ ] Documentation Update
- [ ] Go Version Update
- [ ] Dependency Update

## Description

## Related Tickets & Documents

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- Related Issue #
- Closes #

## Added/updated tests?

- [ ] Yes
- [x] No
- [ ] I need help with writing tests

## Run verifications and test

- [ ] `make verify` is passing
- [ ] `make test` is passing

client.go

@@ -399,7 +399,7 @@ func (d *Dialer) DialContext(ctx context.Context, urlStr string, requestHeader h
 		}
 	}
 
-	if resp.StatusCode != 101 ||
+	if resp.StatusCode != http.StatusSwitchingProtocols ||
 		!tokenListContainsValue(resp.Header, "Upgrade", "websocket") ||
 		!tokenListContainsValue(resp.Header, "Connection", "upgrade") ||
 		resp.Header.Get("Sec-Websocket-Accept") != computeAcceptKey(challengeKey) {

proxy.go

@@ -75,7 +75,7 @@ func (hpd *httpProxyDialer) Dial(network string, addr string) (net.Conn, error)
 		return nil, err
 	}
 
-	if resp.StatusCode != 200 {
+	if resp.StatusCode != http.StatusOK {
 		if err := conn.Close(); err != nil {
 			log.Printf("httpProxyDialer: failed to close connection: %v", err)
 		}