Remove nullable member type from SensorOptions.frequency and fix warning

[alexshalamov]

This PR fixes warning for one of the algorithms and removes ambiguous nullable dictionary member.

Reason to make SensorOptions.frequency non-nullable:

• SensorOptions is already optional in constructor
• Easier to check if SensorOptions.frequency is present, like in construct sensor object.
• No need to add null to a possible set of frequency values, therefore, complicating algorithms.

Right now, passing { frequency: null } would lead to setting sensor_instance.desiredSamplingFrequency to null.

---

Preview | Diff

[alexshalamov]

@rwaldron Do you have any objections for removing nullable specifier?

[alexshalamov]

Did a quick search and could not find any other API that uses nullable primitive (double) in named dictionary that is used as a input.

[alexshalamov]

I'm merging this PR. If there would be any comments, I will address them in follow-up PRs. Thanks!