main/procps: install documentation to subdirectory
Patchset from Sebastian sebastian@sebsite.pw via aports #3860:
procps currently installs its docs into /usr/share/doc, which results in
the files `FAQ` and `bugs.md` being installed directly into
/usr/share/doc rather than a subdirectory. This commit fixes procps to
instead install docs to /usr/share/doc/procps.
Signed-off-by: Sebastian <sebastian@sebsite.pw>