test: remove redundant error check

[alexandear]

This PR simplifies err == nil || err != nil && !strings.EqualFold(err.Error(), "timeout") statement. If the first err is non-nil then the second err is automatically non-nil.

The redundancy is found by govet's nilness check:

❯ ./bin/golangci-lint run
server_test.go:4149:24: nilness: tautological condition: non-nil != nil (govet)
                if err == nil || err != nil && !strings.EqualFold(err.Error(), "timeout") {
                                     ^
server_test.go:4209:24: nilness: tautological condition: non-nil != nil (govet)
                if err == nil || err != nil && !strings.EqualFold(err.Error(), "timeout") {
                                     ^

[erikdubbelboer]

Thanks!