Remove misleading macros from -width arguments

Also, remove $FreeBSD$ tag from manual page examples.

MFC after:	1 week

share/examples/mdoc/example.1

@@ -24,8 +24,6 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\" $FreeBSD$
-.\"
 .\" Note: The date here should be updated whenever a non-trivial
 .\" change is made to the manual page.
 .Dd December 8, 1999
@@ -47,7 +45,7 @@ It is intended that this example can be used as a template
 when writing a new manual page.
 .Pp
 The options are as follows:
-.Bl -tag -width "-d Ar argument"
+.Bl -tag -width "-d argument"
 .It Fl a
 Example optional
 .Fl a

share/examples/mdoc/example.3

@@ -24,8 +24,6 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\" $FreeBSD$
-.\"
 .\" Note: The date here should be updated whenever a non-trivial
 .\" change is made to the manual page.
 .Dd July 30, 2004

share/examples/mdoc/example.4

@@ -24,8 +24,6 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\" $FreeBSD$
-.\"
 .\" Note: The date here should be updated whenever a non-trivial
 .\" change is made to the manual page.
 .Dd July 31, 2015
@@ -81,7 +79,7 @@ Example device 4201
 Example device 4202
 .El
 .Sh FILES
-.Bl -tag -width ".Pa /dev/null" -compact
+.Bl -tag -width "/dev/null" -compact
 .It Pa /dev/null
 Example of a file in the
 .Sx FILES

share/examples/mdoc/example.9

@@ -24,8 +24,6 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\" $FreeBSD$
-.\"
 .\" Note: The date here should be updated whenever a non-trivial
 .\" change is made to the manual page.
 .Dd September 27, 2006