chore: remove ARM support

Building/testing for ARM does not happen often - the only runtime environment is Raspberry PI, which supports ARM64 - and complicates support for a ton of features. Aside from that, CI runs are much longer for ARM Dokku images, often reaching 15-20 minutes or just timing out completely.

Rather than support an architecture that doesn't have much usage by maintainers and has a lot of maintenance burden, we're removing the platform.

plugins/builder-lambda/builder-detect

@@ -9,10 +9,6 @@ trigger-builder-lambda-builder-detect() {
   declare APP="$1" SOURCECODE_WORK_DIR="$2"
   local ARCHITECTURE="$(dpkg --print-architecture 2>/dev/null || true)"
 
-  if [[ "$ARCHITECTURE" == "armhf" ]]; then
-    return
-  fi
-
   if [[ -f "$SOURCECODE_WORK_DIR/lambda.yml" ]]; then
     echo "lambda"
     return