deprecation warning from rlang

[MichaelChirico]

https://github.com/thomasp85/gganimate/blob/989e0e65e74bbaf43457a253318f2a80ad855c74/R/transition-time.R#L149

is throwing a deprecation warning:

Subsetting quosures with [[ is deprecated as of rlang 0.4.0 Please use quo_get_expr() instead.

It looks like quo_get_expr() is a drop-in replacement:

q = quo(ns::foo(x))
identical(q[[2]], rlang::quo_get_expr(q))
# [1] TRUE

Happy to file a PR if that sounds right to you. I can't tell exactly when quo_get_expr() was added to rlang but it seems >=4 years ago, so quite some time.