tests,misc: Removing cloudbuild_presubmit.yaml

This is not used. It can be removed.

Change-Id: I2e25a5407ca70a18b4e619f4e65b69b98c873511
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38375
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

cloudbuild_presubmit.yaml

@@ -1,31 +0,0 @@
-steps:
-
-    - name: 'gcr.io/cloud-builders/docker'
-      entrypoint: 'bash'
-      args:
-      - '-c'
-      - |
-        docker pull gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest \
-        || exit 0
-
-    - name: 'gcr.io/cloud-builders/docker'
-      args: ['build',
-             '-t',
-             'gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest',
-             '--cache-from',
-             'gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest',
-             'util/dockerfiles/ubuntu-18.04_all-dependencies']
-
-    - name: 'gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest'
-      entrypoint: 'scons'
-      args: ['build/NULL/unittests.opt', '-j', '4']
-
-    - name: 'gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest'
-      dir: 'tests'
-      entrypoint: 'python'
-      args: ['main.py', 'run', '-j', '4', '-t', '8', '--length', 'quick']
-
-images: ['gcr.io/$PROJECT_ID/ubuntu-18.04_all-dependencies:latest']
-options:
-      machineType: 'N1_HIGHCPU_8'
-timeout: 18000s # 5 Hours