stop building librdkafka on aarch64

Requirements for confluent-kafka-python are behind what Debian offers so
there is no point in building librdkafka anymore.

Change-Id: Iebb88900ba9a78ba3c2b0348bdc3fca67279bfdf

.zuul.d/jobs.yaml

@@ -60,4 +60,3 @@
     parent: requirements-tox-py38-check-uc
     nodeset: ubuntu-focal-arm64
     timeout: 7200
-    pre-run: playbooks/build-kafka.yaml

playbooks/build-kafka.yaml

@@ -1,43 +0,0 @@
-- hosts: all
-  tasks:
-    - name: Build and install librdkafka 1.4.0+
-      block:
-        - name: Install librdkafka build dependencies
-          apt:
-            name:
-              - liblz4-dev
-              - libsasl2-dev
-              - libssl-dev
-              - libzstd-dev
-              - python3
-              - zlib1g-dev
-              - debhelper
-              - devscripts
-              - wget
-              - build-essential
-            state: present
-            install_recommends: no
-          become: true
-
-        - name: Create build directory
-          tempfile:
-            state: directory
-          register: build_dir
-
-        - name: Fetch librdkafka from Debian 'testing'
-          command: "dget -u https://snapshot.debian.org/archive/debian/20200513T084344Z/pool/main/libr/librdkafka/librdkafka_1.4.2-1.dsc"
-          args:
-            chdir: "{{ build_dir.path }}"
-
-          # NOTE(hrw): use '-d' to skip 'error: Unmet build dependencies: debhelper-compat (= 13)'
-        - name: Build librdkafka package
-          shell:
-            cmd: |
-              set +o errexit
-              set -o xtrace
-
-              debuild -b -d
-              ls -l ../*
-              sudo debi
-            executable: /bin/bash
-            chdir: "{{ build_dir.path }}/librdkafka-1.4.2/"