xblocks: update hashes

requirements/edx/custom.txt

 # Custom requirements to be customized by individual OpenEdX instances
 
--e git+https://github.com/edx-solutions/xblock-mentoring.git@cc2026a4da325937a2e9a7ba8678b75ce4ef5b68#egg=xblock-mentoring
--e git+https://github.com/edx-solutions/xblock-image-explorer.git@9b01df4bca8aca89d300850a357fb1647cbd3173#egg=xblock-image-explorer
+-e git+https://github.com/edx-solutions/xblock-mentoring.git@b59e5e4fb0d75c8a18da0b1a687c674d2e527f50#egg=xblock-mentoring
+-e git+https://github.com/edx-solutions/xblock-image-explorer.git@67f4c249844a2ca3c63513799a1b2a584ea91774#egg=xblock-image-explorer
 -e git+https://github.com/edx-solutions/xblock-drag-and-drop.git@eaa8dd4d934a374738fd7385fc636cbb99575c40#egg=xblock-drag-and-drop
--e git+https://github.com/edx-solutions/xblock-drag-and-drop-v2.git@1e99a60c7f44c0c51f40b90069d911c61a35103b#egg=xblock-drag-and-drop-v2
--e git+https://github.com/edx-solutions/xblock-ooyala.git@10ededa58aab3f8893d98de36e2e5279890064bd#egg=xblock-ooyala
--e git+https://github.com/edx-solutions/xblock-group-project.git@2b932de36e293bd08f6a59112daa9d6794a05c46#egg=xblock-group-project
--e git+https://github.com/edx-solutions/xblock-discussion.git@5b14678ca85856b4db2bb612b69047ec82c11efb#egg=xblock-discussion
--e git+https://github.com/edx-solutions/xblock-adventure.git@7b0b4fae3d1aeab665001a16f42782b9ef9f8ccd#egg=xblock-adventure
+-e git+https://github.com/edx-solutions/xblock-drag-and-drop-v2.git@dbbd3afdf534059ee75d0e6c4f1ea7d750bc4d43#egg=xblock-drag-and-drop-v2
+-e git+https://github.com/edx-solutions/xblock-ooyala.git@81f91e6b03a50907e6838f0494b0bcf14e968a5e#egg=xblock-ooyala
+-e git+https://github.com/edx-solutions/xblock-group-project.git@3c96d3e9bc287048709659ae0dbf4b0923927839#egg=xblock-group-project
+-e git+https://github.com/edx-solutions/xblock-discussion.git@a4ccc0e18b0aca14a3219afaa6ec6e8036821320#egg=xblock-discussion
+-e git+https://github.com/edx-solutions/xblock-adventure.git@30894de41ee7efe7d5b6400086463d12995893f7#egg=xblock-adventure