Add update step in CI

Author: rustaceanrob

.github/workflows/rust.yml

@@ -37,7 +37,9 @@ jobs:
       - uses: extractions/setup-just@v3
       - uses: actions-rust-lang/setup-rust-toolchain@v1
       - name: "Install Bitcoin dependencies"
-        run: sudo apt-get install build-essential cmake pkgconf python3 libevent-dev libboost-dev
+        run: |
+          sudo apt-get update
+          sudo apt-get install build-essential cmake pkgconf python3 libevent-dev libboost-dev capnproto libcapnp-dev
       - name: "Run test suite"
         run: just test