Revert "ci: Release and test with Rust 1.78 instead of stable"

This reverts commit 4448e37d98.

.github/workflows/release_nightly.yml

@@ -108,9 +108,7 @@ jobs:
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable
         with:
-          # TODO: Return to latest "stable" once this is released:
-          # https://github.com/gfx-rs/wgpu/pull/5831 (probably in wgpu 0.20.2)
-          toolchain: "1.78"
+          toolchain: stable
           targets: ${{ matrix.target }}
 
       - name: Install Linux dependencies

.github/workflows/test_rust.yml

@@ -38,9 +38,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # TODO: Return to latest "stable" once this is released:
-        # https://github.com/gfx-rs/wgpu/pull/5831 (probably in wgpu 0.20.2)
-        rust_version: ["1.78"]
+        rust_version: [stable]
         os: [ubuntu-22.04, windows-latest, macos-14]
         include:
           - rust_version: nightly
@@ -182,9 +180,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        # TODO: Return to latest "stable" once this is released:
-        # https://github.com/gfx-rs/wgpu/pull/5831 (probably in wgpu 0.20.2)
-        rust_version: ["1.78"]
+        rust_version: [stable]
         os: [ubuntu-22.04, windows-latest, macos-14]
         include:
           - rust_version: nightly