Stop pinning once_cell in CI

Apparently `proptest` has dropped its `once_cell` dependency, and
we thus no longer need to pin it.

Author: TheBlueMatt

ci/ci-tests.sh

@@ -21,9 +21,6 @@ PIN_RELEASE_DEPS # pin the release dependencies in our main workspace
 # The addr2line v0.21 crate (a dependency of `backtrace` starting with 0.3.69) relies on rustc 1.65
 [ "$RUSTC_MINOR_VERSION" -lt 65 ] && cargo update -p backtrace --precise "0.3.68" --verbose
 
-# The once_cell v1.21.0 crate (a dependency of `proptest`) relies on rustc 1.70
-[ "$RUSTC_MINOR_VERSION" -lt 70 ] && cargo update -p once_cell --precise "1.20.3" --verbose
-
 # proptest 1.3.0 requires rustc 1.64.0
 [ "$RUSTC_MINOR_VERSION" -lt 64 ] && cargo update -p proptest --precise "1.2.0" --verbose