prepalldocs: fix inverted eapi_has_docompress

This broke in commit ab46499322311c1faa710c63d0a5339e49a9061a.
diff --git a/bin/ebuild-helpers/prepalldocs b/bin/ebuild-helpers/prepalldocs
index b76f084..3094661 100755
--- a/bin/ebuild-helpers/prepalldocs
+++ b/bin/ebuild-helpers/prepalldocs
@@ -4,7 +4,7 @@
 
 source "${PORTAGE_BIN_PATH:-/usr/lib/portage/bin}"/isolated-functions.sh
 
-if ! ___eapi_has_docompress; then
+if ___eapi_has_docompress; then
 	die "'${0##*/}' has been banned for EAPI '$EAPI'"
 	exit 1
 fi