Remove installation of Bundler 1.17 from Docker image
We do not need bundler 1.x since we got rid of at 1.x at !1273 (merged).
Relates to !1418 (merged)
Edited by Takuya Noguchi
We do not need bundler 1.x since we got rid of at 1.x at !1273 (merged).
Relates to !1418 (merged)