fix: dont undo if not done

[bboynton97]

If stop_instrumenting() is called when instrumenting has not be set up, the code would replace all of the provider completion functions with None.

This fixes that and only undoes instrumentation if it has been set up already.

Not related, but #256 made me think about this and catch the bug before it came up!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 26 lines in your changes missing coverage. Please review.

Files	Patch %	Lines
agentops/llms/litellm.py	0.00%	7 Missing ⚠️
agentops/llms/cohere.py	0.00%	5 Missing ⚠️
agentops/llms/openai.py	0.00%	5 Missing ⚠️
agentops/llms/anthropic.py	0.00%	4 Missing ⚠️
agentops/llms/groq.py	0.00%	4 Missing ⚠️
agentops/llms/ollama.py	0.00%	1 Missing ⚠️

Flag	Coverage Δ
unittests	43.45% <0.00%> (-0.10%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
agentops/llms/ollama.py	25.31% <0.00%> (ø)
agentops/llms/anthropic.py	12.58% <0.00%> (-0.09%)	⬇️
agentops/llms/groq.py	16.51% <0.00%> (-0.16%)	⬇️
agentops/llms/cohere.py	14.00% <0.00%> (-0.10%)	⬇️
agentops/llms/openai.py	13.88% <0.00%> (-0.10%)	⬇️
agentops/llms/litellm.py	15.21% <0.00%> (-0.12%)	⬇️