Set C++ standard in `pineappl_applgrid` #75

Job	Run time
cli-linux (x86_64-unknown-linux-gnu)	3m 32s
capi-macos (x86_64-apple-darwin)	8m 42s
cli-macos (macos-latest, x86_64-apple-darwin)	4m 22s
capi-macos (aarch64-apple-darwin)	7m 46s
capi-linux (x86_64-unknown-linux-gnu)	2m 15s
cli-macos (macos-14, aarch64-apple-darwin)	4m 3s
create-release	0s
publish-crates	0s
wheels-eol-linux (x86_64)	1m 30s
wheels-linux (x86_64)	4m 51s
wheels-macos (aarch64)	7m 14s
wheels-sdist	16s
wheels-windows (x64)	7m 3s
wheels-macos (x86_64)	6m 38s
publish-release	0s
Release	0s
	58m 12s

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