This reverts changes made to `mlir/lib/Tools/PDLL/Parser/Parser.cpp` in
095b41c6eedb3acc908dc63ee91ff77944c07d75 .
`raw_indented_ostream::printReindented()` reads from a string to which
it also concurrently writes to, causing unintended behavior.
Credits to @jackalcooper for finding the issue.
05484c6333