testsuite: Mark hs_try_putmvar003 as fragile in threaded1
testsuite: Mark hs_try_putmvar003 as fragile in threaded1

Due to #16361. Note that I'm leaving out threaded2 since it's not clear
whether the single crash in that way was due to other causes.

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc