Suppress only some warnings in PMF formatting

[zsusswein]

For EpiNow2 in the *_format() functions.

I originally wrote:

I also want to flag this choice as a to-discuss. EpiNow2 throws a "once every 8 hours" warning about the change in the use of the max argument. This warning gets thrown every time on CI and causes a failing R CMD check.

I had trouble getting rlang::try_fetch() to downgrade the warning to a message, so I gave up and just suppressed the warning.

I think this choice is reasonable because we're running on a pinned version of the package. We should be able to catch any issues in a managed upgrade on CI. But if we for some reason think interactive use with multiple versions of EpiNow2 is needed, we should revisit this choice.

We landed on:

Yes seems correct that 1. We don't want to get this warning 2. We do want to get other warnings (probably). As to how to achieve that technically I'm unsure

Originally posted by @athowes in #26 (comment)

[athowes]

Presumably one could regex that specific warning and stop it (and let others through) but that seems quite an ugly solution.

[zsusswein]

We should follow the procedure I worked out here: https://github.com/CDCgov/cfa-gam-rt/blob/409060c906664b412d2b427d033ea18ae6633329/R/predict.R#L673