Update minimum Rust version in CI to 1.43.0.

Firefox currently requires vendored Rust code (including Cranelift) to
compile on Rust 1.43.0, according to this line:

https://searchfox.org/mozilla-central/rev/eb9d5c97927aea75f0c8e38bbc5b5d288099e687/python/mozboot/mozboot/util.py#16

Whenever that version is updated, we can bump this CI check's Rust
version accordingly.

.github/workflows/main.yml

@@ -124,12 +124,12 @@ jobs:
     - run: cargo check --target wasm32-unknown-emscripten -p wasi-common
     - run: cargo check --target armv7-unknown-linux-gnueabihf -p wasi-common
 
-    # Check that codegen and wasm crates typecheck on 1.41.0; this is required
+    # Check that codegen and wasm crates typecheck on 1.43.0; this is required
     # for Firefox.
-    - run: rustup install 1.41.0
-    - run: cargo +1.41.0 check -p cranelift-codegen
-    - run: cargo +1.41.0 check -p cranelift-wasm
-    - run: cargo +1.41.0 check -p cranelift-tools
+    - run: rustup install 1.43.0
+    - run: cargo +1.43.0 check -p cranelift-codegen
+    - run: cargo +1.43.0 check -p cranelift-wasm
+    - run: cargo +1.43.0 check -p cranelift-tools
 
 
   fuzz_targets: