httr -> httr2

[sckott]

• vcr on cran only has support for httr, not httr2. httr2 support is in the works but not ready quite yet.
• this package uses vcr.
• which means we need to use httr in this pkg for now

move to httr2 once vcr has support for it on github at least (& cran before this pkg goes to cran)

see also https://github.com/getwilds/proofr/issues/3