Inconsistent use of full stop in error messages

[stefanoborini]

Trivial thing, but it bugs me a lot because users get inconsistent writing style for the error messages they receive

in sv_gte, the message has a full stop at the end of the message:

https://github.com/rstudio/shinyvalidate/blob/1c642658b341b1413aa7c4fd766cc53ced0cc7b6/R/rules.R#L901

in sv_integer, there's no full stop

https://github.com/rstudio/shinyvalidate/blob/1c642658b341b1413aa7c4fd766cc53ced0cc7b6/R/rules.R#L576C1-L576C1

These two are examples. The issue is pretty much all over the place.