Merge bitcoindevkit/bdk#1137: fix: Add the pinning of time/cc in README

Merge bitcoindevkit/bdk#1137: fix: Add the pinning of time/cc in README

f28e665c7dd1d929f0b4f80a79caecafaf4b385e ci: update code_coverage workflow to use rust stable version (Steve Myers)
edfd4c236d76c91b3599c333ae8456ed4f577064 fix: Add the pinning of time/cc in README (Daniela Brozzoni)

Pull request description:

  Should have been in #1135, sorry.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  notmandatory:
    ACK f28e665c7dd1d929f0b4f80a79caecafaf4b385e

Tree-SHA512: e1c2c05f436da1fd59b9988628318c0563b2dbe85a5f4fb8aef4c35d7601c441a542e8a2c3591c02f3a05ad9456cfc2d3f5e8605064498a56a39766f5bcbc2e1