Fix an infinite loop in C++ Mode when we have "{ .... [ .... }"

Fix an infinite loop in C++ Mode when we have "{ .... [ .... }"

* lisp/progmodes/cc-fonts.el (c-font-lock-c++-lambda-captures): In the inner
`while' form's condition, check for "\\s)" rather than merely "\\]", so that
the loop won't hang at a "terminating" paren of a different type (due to the
c-syntactic-re-search-forward at the end of the loop stopping at such
characters).