Increase sleep in test algorithm

[jclarkeSTFC]

This test fails intermittently, but I can't reproduce it, even when building with the CI cmake configuration and running the test 100 times. My best guess is that when the test asserts that the algorithm hasn't finished yet, e.g. here, it was so quick that it has finished, so I've increased the sleep in the test algorithm from 1 ms to 10 ms to make it take longer (but still not long).

If the test continues to fail randomly after this then we can go back to #37760

Fixes #37760.

To test:

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[thomashampson]

Let's get this in and keep an eye on the unit test monitor to see if it has made a difference:
https://mantidproject.github.io/unittest-monitor/Linux_table.html

[RichardWaiteSTFC]

Looks good, 10 ms is not long at all relative to how long other tests take right?
Maybe you could have made it even longer, but it's difficult to know if you can't reproduce it, so lets see how we get on!