chore!: drop "timer" option to startTransaction/startSpan

[trentm]

Closes: #2990

[david-luna]

Should we warn about the agent ignoring/removing the option so app devs can drop it in their apps config?

[trentm]

can drop it in their apps config?

I might be misunderstanding you, but this isn't an app config thing. This could only impact a user if they were doing:

apm.startSpan('my-span-name', {timer: <some custom Timer object>})

where that timer option was never documented.

[david-luna]

Thanks for the clarification :)