Use a fixed rust version so there are no clippy surprises during CI

Author: nojaf

.github/workflows/ci.yml

@@ -116,7 +116,7 @@ jobs:
         if: steps.rewatch-build-cache.outputs.cache-hit != 'true'
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: stable
+          toolchain: 1.88.0
           targets: ${{ matrix.rust-target }}
 
       - name: Build rewatch

rewatch/Cargo.toml

@@ -2,7 +2,7 @@
 name = "rescript"
 version = "12.0.0-beta.12"
 edition = "2024"
-rust-version = "1.85"
+rust-version = "1.88"
 
 [dependencies]
 ahash = "0.8.3"