install: don't install man page twice
install: don't install man page twice

Looks like a merge conflict in 77ed12f left in the old, unconditional
install rule. Remove it, the new and improved rule is a few lines down.

Fixes #5044.

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node