Bump UBC Peer Instruction xblock to v0.5.3
Bump UBC Peer Instruction xblock to v0.5.3

Stanford-Online/edx-platform,Stanford-Online/edx-platform,caesar2164/edx-platform,Stanford-Online/edx-platform,caesar2164/edx-platform,caesar2164/edx-platform,Stanford-Online/edx-platform,caesar2164/edx-platform