update to httr2

[christopherkenny]

Please ensure the following before submitting a PR:

• if suggesting code changes or improvements, open an issue first
• for all but trivial changes (e.g., typo fixes), add your name to DESCRIPTION
• for all but trivial changes (e.g., typo fixes), documentation your change in NEWS.md with a parenthetical reference to the issue number being addressed
• if changing documentation, edit files in /R not /man and run devtools::document() to update documentation
• add code or new test files to /tests for any new functionality or bug fix
• make sure R CMD check runs without error before submitting the PR

Note: I have not edited the tests, as there are no new features, just internal changes, but the existing tests pass.

addresses #142

[pdurbin]

@christopherkenny hi! If you want this PR to close that issue you should change "addresses" to "closes" (or another keyword). But only if you do! Thanks for the PR! ❤️

[kuriwaki]

Great -- I went ahead and made the attribution myself. Will try it out.

[christopherkenny]

Thanks @pdurbin. Appreciate the tip. And thanks, Shiro.