chore: pin workflows to specific ubuntu versions #723

Job	Run time
Check for unneeded dependencies	59s
Benchmarks	7m 15s
Build (x86_64/linux)	1m 6s
Source code checks (stable)	33s
Build (aarch64/macos)	1m 1s
Source code checks (1.75.0)	39s
Build (aarch64/linux)	1m 37s
Test (linux)	1m 38s
Build (wasm32/wasi-0.2)	46s
Test (macOS)	1m 59s
Build (x86_64/windows)	1m 31s
OS target tests (Fedora/latest)	27s
OS target tests (Debian/latest)	15s
OS target tests (Arch Linux/latest)	20s
	20m 6s

Provide feedback