Don't leak CXStrings for replacement fix-its in c-index-test.

The loop body used to contain a switch statement; it looks like r96685 replaced
that with an if/else if/else but accidentally left one of the three break
statements from the switch behind, skipping the clang_disposeString() call
for replacements (and the rest of the loop too, which apparently doesn't make
a differences for the test cases we have).

r96685: http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20100215/027754.html

This too might possibly the last leak in clang (PR19521).