doc: convert the remaining legacy syntax

The block conversion changed the bodies of the reference sections but
left every "**Syntax:**" header spelling the line-based format, so each
page opened by teaching the format it then stopped using.  Six files
were missed entirely: runparts, files, capabilities, requirements,
runlevels, and switchroot.

runparts had no block spelling written down anywhere, though the parser
has read `runparts`, `runparts-progress`, and `runparts-sysv` all along.

tty gains a table per variant.  Its three syntax lines carried nine
positional fields between them, which no longer describes anything the
parser accepts.

Fixes #148

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/config/service-sync.md

@@ -43,8 +43,8 @@ like this:
     service bar       { notify = "s6"       command = "bar"       }
     service qux       { notify = "none"     command = "qux"       }
 
-The `notify:none` syntax is for completeness in systems which run in
-`readiness pid` mode (default).  Services declared with `notify:none`
+The `notify = "none"` setting is for completeness in systems which run in
+`readiness pid` mode (default).  Services declared with `notify = "none"`
 will transition to ready as soon as Finit has started them, e.g.,
 `service/qux/ready`.