chore: update rust version to 1.70.0 #73

Job	Run time
Run checks (ubuntu-latest)	2m 28s
Run checks (macos-latest)	4m 12s
Run checks (windows-latest)	7m 24s
Run tests (ubuntu-latest)	1m 2s
Build library (linux-aarch64, ubuntu-latest, libindy_credx.so, aarch64-unknown-linux-gnu, true)	3m 17s
Run tests (macos-latest)	2m 45s
Build library (linux-x86_64, ubuntu-latest, libindy_credx.so, x86_64-unknown-linux-gnu, true)	3m 20s
Run tests (windows-latest)	2m 20s
Build library (darwin-universal, macos-latest, libindy_credx.dylib, darwin-universal, beta)	5m 45s
Build library (windows-x86_64, windows-latest, indy_credx.dll, x86_64-pc-windows-msvc)	8m 27s
Build and test Python wrapper (linux-aarch64, 3.8)	19s
Build and test Python wrapper (linux-x86_64, 3.8)	42s
Build and test Python wrapper (darwin-universal, 3.8)	27s
Build and test Python wrapper (windows-x86_64, 3.8)	1m 41s
	44m 9s

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