external/lowdown: remove.

Every distribution we have packages this now.

Changelog-Changed: Build: lowdown is now required (we no longer bundle our own).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

.github/workflows/bsd.yml

@@ -60,7 +60,7 @@ jobs:
           git clone https://github.com/lightning/bolts.git ../bolts
           # fatal: unsafe repository ('/Users/runner/work/lightning/lightning' is owned by someone else)
           git config --global --add safe.directory `pwd`
-          for d in libsodium libwally-core gheap jsmn libbacktrace lowdown; do git config --global --add safe.directory `pwd`/external/$d; done
+          for d in libsodium libwally-core gheap jsmn libbacktrace; do git config --global --add safe.directory `pwd`/external/$d; done
           git submodule update --init --recursive
 
           ./configure CC="$CC" --disable-valgrind

.github/workflows/ci.yaml

@@ -196,7 +196,6 @@ jobs:
         run: |
           bash -x .github/scripts/setup.sh
           sudo apt-get update -qq
-          sudo apt-get install -y -qq lowdown
           # We're going to check BOLT quotes, so get the latest version
           git clone https://github.com/lightning/bolts.git ../${BOLTDIR}
 

.github/workflows/macos.yaml

@@ -37,7 +37,7 @@ jobs:
         run: |
           export PATH="/usr/local/opt:/Users/runner/.local/bin:/opt/homebrew/bin/python3.10/bin:$PATH"
 
-          brew install gnu-sed autoconf automake libtool protobuf openssl
+          brew install gnu-sed autoconf automake libtool protobuf openssl lowdown
 
           # https://github.com/grpc/grpc/issues/31737#issuecomment-1323796842
           export GRPC_PYTHON_BUILD_SYSTEM_OPENSSL=1