ci: No need to add the llvm repository for wasm

Adding it fails with "The repository'http://apt.llvm.org/focal
llvm-toolchain-focal Release' does not have a Release file.", and for
some reason it's not needed anymore.

Author: danielabrozzoni

.github/workflows/cont_integration.yml

@@ -71,7 +71,6 @@ jobs:
         uses: actions/checkout@v2
         # Install a recent version of clang that supports wasm32
       - run: wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add - || exit 1
-      - run: sudo apt-add-repository "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-10 main" || exit 1
       - run: sudo apt-get update || exit 1
       - run: sudo apt-get install -y libclang-common-10-dev clang-10 libc6-dev-i386 || exit 1
       - name: Install Rust toolchain