CI/CD: `TestBittrexWebsocket` takes too long

[ukane-philemon]

Tests keep failing on #1979 but it's not related to that PR.

?   	github.com/decred/dcrdata/exchanges/v3/ratesproto	[no test files]
2024-01-05 13:09:55.597 [ERR] EXE: poloniex websocket error: closed (expected)
2024-01-05 13:09:55.700 [TRC] EXE: Initializing websocket connection for bittrex
2024-01-05 13:14:55.853 [ERR] EXE: bittrex websocket error: negotiate failed: request failed: 403 Forbidden
2024-01-05 13:14:55.853 [TRC] EXE: last bittrex websocket update 300.153 seconds ago
2024-01-05 13:14:55.853 [TRC] EXE: using http fallback for bittrex orderbook data
panic: test timed out after 10m0s
running tests:
	TestBittrexWebsocket (10m0s)