CI: move conda build tests back to allowed failures (#19196)

Author: jreback

.travis.yml

@@ -49,6 +49,7 @@ matrix:
         apt:
           packages:
           - python-gtk2
+    # In allow_failures
     - dist: trusty
       env:
         - JOB="3.5_CONDA_BUILD_TEST" TEST_ARGS="--skip-slow --skip-network" CONDA_BUILD_TEST=true
@@ -76,6 +77,9 @@ matrix:
       env:
         - JOB="3.6_DOC" DOC=true
     allow_failures:
+      - dist: trusty
+        env:
+          - JOB="3.5_CONDA_BUILD_TEST" TEST_ARGS="--skip-slow --skip-network" CONDA_BUILD_TEST=true
       - dist: trusty
         env:
           - JOB="2.7_SLOW" SLOW=true