You can increase the pandoc's default stack size using +RTS -Ksize -RTS
in your command as follows:
pandoc +RTS -K100000000 -RTS run_faster.html -f html -t mediawiki -s -o
This will increase pandoc's stack size from 16,777,216 bytes to 100,000,000 bytes.
If you get the same error try again with a larger stack size.
If you get a different error then your copy of pandoc might not have been compiled with --ghc-options=-rtsopts=all