Add a note about target precision

[jyu00]

URL to the relevant guide or resource

https://quantum.cloud.ibm.com/docs/en/guides/estimator-options

Select all that apply

• new content request
• typo
• code bug
• out-of-date content
• broken link
• other

Describe the fix or the content request.

We should add a note saying that the precision parameter specifies the target precision, meaning we will try but it's not guaranteed that we'll reach that precision.

For new content requests - if the request is accepted, do you want to write the content?

I only want to review the material when it's finished