fix: filter None values from OpenTelemetry attributes

[galz10]

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Fixes #1385 🦕

[tswast]

@galz10 If you look at the Kokoro output, there are some related failing tests that need to be investigated / fixed.

[galz10]

@galz10 If you look at the Kokoro output, there are some related failing tests that need to be investigated / fixed.

Yea saw those, planning to fix those today