Add a bug to the prophet pin (#1209)

http:https://b/266272046

Dockerfile.tmpl

@@ -312,6 +312,7 @@ RUN pip install mpld3 && \
  pip install pyexcel-ods && \
  pip install sklearn-pandas && \
  pip install stemming && \
+ # b/266272046 prophet 1.1.2 breaks the test
  pip install prophet==1.1.1 && \
  pip install holoviews && \
  pip install geoviews && \