`dev_sitrep()` in Positron

[maelle]

When running devtools::dev_sitrep() in Positron, there's a message about the RStudio version because devtools:::is_rstudio_running() returns TRUE.

Could this be avoided?

Should devtools check the Positron version instead in this case?

[hadley]

@jennybc how hard would this be to fix with current tools? It should just be a matter of changing the header, right? (The actual version looks fine to me)