ci-dockerfiles-sanity-check: Disable single-value matrix axis

It's unclear why it's being used, as originally this single-value
config was built on the same host as the parent job (build-amd64).
As we switch to build-amd64-private, just drop this axis at all.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I31f4053e9dad59cf64489a24a9f43801e7b3ed7d
diff --git a/ci-dockerfiles-sanity-check.yaml b/ci-dockerfiles-sanity-check.yaml
index f51e4e0..845ab65 100644
--- a/ci-dockerfiles-sanity-check.yaml
+++ b/ci-dockerfiles-sanity-check.yaml
@@ -65,12 +65,12 @@
                     - branch-compare-type: 'PLAIN'
                       branch-pattern: 'master'
             silent-start: false
-    axes:
-        - axis:
-            type: slave
-            name: label
-            values:
-                - build-amd64
+#    axes:
+#        - axis:
+#            type: slave
+#            name: label
+#            values:
+#                - build-amd64
     execution-strategy:
         sequential: false
     wrappers: