Tests

fix: MSRV has changed for various reasons #63

Job	Run time
ubuntu-latest w/ bindgen (R-devel rust-stable )	4m 42s
windows-latest (R-release rust-stable-msvc)	14m 20s
macOS-latest w/ bindgen (R-devel rust-stable )	5m 27s
windows-latest (R-devel rust-stable-msvc)	13m 57s
windows-latest w/ bindgen (R-release rust-stable-msvc x86_64-pc-windows-gnu)	6m 8s
windows-latest (R-oldrel rust-stable-msvc)	15m 2s
windows-latest w/ bindgen (R-devel rust-stable-msvc x86_64-pc-windows-gnu)	5m 51s
macOS-latest (R-release rust-stable)	9m 20s
windows-latest w/ bindgen (R-release rust-nightly-msvc x86_64-pc-windows-gnu)	7m 35s
ubuntu-latest (R-release rust-stable)	5m 59s
windows-latest w/ bindgen (R-oldrel rust-nightly-msvc x86_64-pc-windows-gnu)	12m 29s
ubuntu-latest (R-release rust-nightly)	6m 21s
ubuntu-latest (R-devel rust-stable)	7m 56s
ubuntu-latest (R-oldrel rust-stable)	6m 7s
	2h 1m 14s

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