Remove indent workaround in man page RST sources

docutils 0.10 properly adds indentation to example blocks in man
pages, so we do not need to force an extra indentation level.  Get rid
of the workaround wherever we use it.

(back ported from 4bd50f73c80a86852ec0879abdf52202be40892b)

ticket: 7954
version_fixed: 1.12.2
status: resolved