Revert "Add support for test.valgrind parallel testing"

This reverts commit f0aff2daa44923f600f6e1f2429a2add2214a9d5
"Add support for test.valgrind parallel testing"

This patch was accidentally pushed (by me); it breaks some things.  We
will wait to add this support until after 5.20
perlrebackslash, perlreref.pod: White space only

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