ci: fix rev to be ref when pinning bitcoin-maintainer-tools

Apparently the `checkout` action will just grab random shit in the case
that you configure it with an unknown key. There is a warning in the
middle of the CI output so ok, I guess there's that.

This commit does not change the pinned version of
rust-bitcoin-maintainer-tools, though we do want to update the pin,
because I want to make sure that the pin is actually working.

.github/workflows/rust.yml

@@ -34,7 +34,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@stable
@@ -58,7 +58,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@v1
@@ -83,7 +83,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@stable
@@ -109,7 +109,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@v1
@@ -136,7 +136,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@stable
@@ -160,7 +160,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@v1
@@ -186,7 +186,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: rust-bitcoin/rust-bitcoin-maintainer-tools
-          rev: b2ac115
+          ref: b2ac11556708cd0fb82c8139ff38b1be8d4a62e1
           path: maintainer-tools
       - name: "Select toolchain"
         uses: dtolnay/rust-toolchain@v1