merge-release-branch.yml workflow failing for zenoh-c

[diogomatsubara]

Describe the bug

merge-release-branch.yml failed to merge zenoh-c release branch back into main

See https://github.com/eclipse-zenoh/ci/actions/runs/24405301060/job/71414010140 for the failure and the manually created PR to merge to the changes: eclipse-zenoh/zenoh-c#1268

Initial investigation shows there are 2 fixes required here:

1. fix the update Cargo.toml.in step in the merge-release-branch.yml workflow to find the correct zenoh-c dir checked out in the previous step and avoid /home/runner/work/_temp/e8451fbc-20b0-4c40-af5a-eb10c3134385.sh: line 1: cd: zenoh-c: No such file or directory
2. fix the drift between Cargo.toml.in and Cargo.toml due to the commented out zenoh-pinned-deps-1-75 as per eclipse-zenoh/zenoh-c@258cc37

To reproduce

See https://github.com/eclipse-zenoh/ci/actions/runs/24405301060/job/71414010140

System info

Github Actions ubuntu-latest runner

[diogomatsubara]

Fix 1 was done in #471 and fix 2 was done on #472