test(preflight): fail TestPreflightAzure cleanly on errors

[lokesh-vadlamudi]

Switch the two error checks in TestPreflightAzure from assert.NoError to require.NoError (after azure.New and preflight.Run()).

assert.NoError only records the failure and lets the test continue, so when preflight.Run() returns an error (e.g. an expired Azure client secret), execution fell through to result.Caller.ObjectID on a nil result and panicked:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0]
    integration/preflight_azure_test.go:36

That SIGSEGV aborts the entire integration test binary with exit code 2, taking down the whole shard instead of reporting a single readable test failure. require.NoError stops the test at the error, so the failure surfaces as:

Error: Received unexpected error: failed to get token: ... AADSTS7000222: ... expired ...

The value assertions below are left as assert (they do not dereference nil once result is non-nil). testify/require is vendored since the repo builds with -mod=vendor.