[CI] Move premerge buildbot script to annotated builders

This is where all of the other annotated builder scripts live, so move it
over there.

Reviewers: Keenuts, cmtice, lnihlen, dschuff, gburgessiv

Pull Request: llvm#537

Author: boomanaiden154

premerge/buildbot/Dockerfile

@@ -4,7 +4,6 @@ COPY requirements.lock.txt /requirements.lock.txt
 RUN pip3 install --break-system-packages -r /requirements.lock.txt && rm /requirements.lock.txt
 RUN mkdir /app
 WORKDIR /app
-COPY dispatch_job.py .
 COPY startup.sh .
 RUN chmod +x startup.sh
 ENTRYPOINT /app/startup.sh