shell: grant access to /proc/version

Addresses this denial during CtsBionicTestCases:
avc: denied { getattr } for path="/proc/version" dev="proc"
ino=4026532359 scontext=u:r:shell:s0 tcontext=u:object_r:proc_version:s0
tclass=file permissive=0

Bug: 68067856
Test: cts-tradefed run commandAndExit cts -m CtsBionicTestCases
--skip-all-system-status-check --primary-abi-only --skip-preconditions
No more denials to /proc/version
Change-Id: I7e927fbaf1a8ce3637e09452cbd50f475176838e