Remove files moved to the ansible/awx-ee repo

These have been moved to:

https://github.com/ansible/awx-ee

that will be the home for the processes needed to
build this execution environment.

execution-environment.yml

@@ -1,11 +0,0 @@
----
-version: 1
-dependencies:
-  galaxy: requirements/collections_requirements.yml
-  system: requirements/bindep_requirements.txt
-additional_build_steps:
-  prepend:
-    - RUN pip3 install --upgrade pip setuptools
-  append:
-    - COPY --from=quay.io/project-receptor/receptor /usr/bin/receptor /usr/bin/receptor
-    - RUN mkdir -m 0770 /var/run/receptor

requirements/bindep_requirements.txt

@@ -1,2 +0,0 @@
-subversion [platform:rpm]
-subversion [platform:dpkg]