Try to move rust CI back to 1.70

1.71 seems to have weird issues on Github Actions and that makes the
tests fail for no good reason

(gosh dangit YAML)

.github/workflows/rust_checks.yml

@@ -14,9 +14,13 @@ jobs:
     - name: SetupRust
       uses: ATiltedTree/setup-rust@v1
       with:
-        rust-version: stable
+        # FIXME: We want "stable" here, but 1.71 isn't working
+        # DATE: 2023-07-14
+        rust-version: "1.70"
     - name: cargo fmt
       run: |
+        # Hack: setup-rust seems to fail to install this?
+        rustup component add rustfmt
         cd fish-rust
         cargo fmt --check --all
 
@@ -28,7 +32,9 @@ jobs:
     - name: SetupRust
       uses: ATiltedTree/setup-rust@v1
       with:
-        rust-version: stable
+        # FIXME: We want "stable" here, but 1.71 isn't working
+        # DATE: 2023-07-14
+        rust-version: "1.70"
     - name: Install deps
       run: |
         sudo apt install gettext libncurses5-dev libpcre2-dev python3-pip tmux
@@ -38,5 +44,7 @@ jobs:
         cmake -B build
     - name: cargo clippy
       run: |
+        # Hack: setup-rust seems to fail to install this?
+        rustup component add clippy
         cd fish-rust
         cargo clippy --workspace --all-targets -- --deny=warnings