shiny_file breaks with development version of shiny

[cpsievert]

I noticed this our revdepchecks with our shiny 1.7.2 release candidate (which adds a new argument to shiny::fileInput()):

> ymlthis::shiny_file(label = "file", multiple = TRUE)
Error: Mapped vectors must have consistent lengths:
* `.x` has length 6
* `.y` has length 7

Looks as though all the ymlthis::shiny_*() functions are susceptible to breakage if shiny adds arguments