[Parser] Correct typo after lambda capture initializer is parsed.

This patch fixes an assertion that is triggered when RecordLayoutBuilder
tries to compute the size of a field (for capture "name" in the test
case) whose type hasn't been deduced. The patch fixes the bug by
correcting the typo of the capture initializer after the initializer is
parsed and before setting the expression for the annotation token.

Fixes PR30566.

rdar://problem/23380132

Differential Revision: https://reviews.llvm.org/D25206

llvm-svn: 290156