Revert "ci, docker: Fix LLVM repository signature failure" #1828

This reverts commit 0ffb1749a5811bb63902f00c9fa73b49588d0557, as the underlying issue has been resolved.

The apt repo remains broken in a different way:

$ apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y ca-certificates
$ apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y wget &&     wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc &&     . /etc/os-release && echo "deb http://apt.llvm.org/${VERSION_CODENAME} llvm-toolchain-${VERSION_CODENAME} main" >> /etc/apt/sources.list &&     apt-get update &&     LLVM_VERSION=$(apt-cache search --names-only '^clang-[0-9]+$' | sort -V | tail -1 | cut -f1 -d" " | cut -f2 -d"-" ) &&     DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y "clang-${LLVM_VERSION}" "libclang-rt-${LLVM_VERSION}-dev" &&     ln -s "/usr/bin/clang-${LLVM_VERSION}" /usr/bin/clang-snapshot &&     apt-get autoremove -y wget &&     apt-get clean && rm -rf /var/lib/apt/lists/* 
<snip>
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/libllvm23_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/libclang-cpp23_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/libclang-common-23-dev_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/llvm-23-linker-tools_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/libclang1-23_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/clang-23_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Failed to fetch https://apt.llvm.org/trixie/pool/main/l/llvm-toolchain-snapshot/libclang-rt-23-dev_23%7e%2b%2b20260211082823%2b1e42c76d6133-1%7eexp1%7e20260211082946.371_amd64.deb  404  Not Found [IP: 146.75.74.49 443]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

See https://github.com/llvm/llvm-project/issues/182462

See llvm/llvm-project#182462

It seems to be fixed :)

ACK 76e92cfeeaf67aa3fd780f83e780b92518012c84