Remove depot_tools repo (sonic-net#16114)

It appears that this was initially added to provide the git-retry
command (which doesn't appear to be used today). However, this repo is
now also providing bazel (which is actually used in our build today),
and this command (along with git-retry) expects some vpython3 binary to
be set up/installed.

Rather than going through that, just get rid of this repo.

sonic-slave-bullseye/Dockerfile.j2

@@ -569,10 +569,6 @@ RUN cd /usr/src/gtest && cmake . && make -C /usr/src/gtest
 RUN mkdir /var/run/sshd
 EXPOSE 22
 
-# Install depot-tools (for git-retry)
-RUN git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git /usr/share/depot_tools
-ENV PATH /usr/share/depot_tools:$PATH
-
 # Install dependencies for dhcp relay test
 RUN pip3 install parameterized==0.8.1
 RUN pip3 install pyfakefs