Update lightncandy

This matches upstream trunk at 131696af11 [1]. This solves a double
encoding issue in with subexpressions, which is exposed in
the topic reply placeholder text.

[1] https://github.com/zordius/lightncandy/commit/
  131696af113056dcec74693d18aa947d642c5e57

Change-Id: I7adf717157677d5dcd5546e4a84b02662c8c60de