lpr: fix -o sides example (#8170)

* lpr: updated

`lpr --help` yields:
`Usage: lpr [options] [file(s)]
Options:
-# num-copies           Specify the number of copies to print
-E                      Encrypt the connection to the server
-H server[:port]        Connect to the named server and port
-m                      Send an email notification when the job completes
-o option[=value]       Specify a printer-specific option
-o job-sheets=standard  Print a banner page with the job
-o media=size           Specify the media size to use
-o number-up=N          Specify that input pages should be printed N-up (1, 2, 4, 6, 9, and 16 are supported)
-o orientation-requested=N
                        Specify portrait (3) or landscape (4) orientation
-o print-quality=N      Specify the print quality - draft (3), normal (4), or best (5)
-o sides=one-sided      Specify 1-sided printing
-o sides=two-sided-long-edge
                        Specify 2-sided portrait printing
-o sides=two-sided-short-edge
                        Specify 2-sided landscape printing
-P destination          Specify the destination
-q                      Specify the job should be held for printing
-r                      Remove the file(s) after submission
-T title                Specify the job title
-U username             Specify the username to use for authentication`

Here, it says that that in stead of underscores at two_sided_long_edge, it should have dashes, two-sided-long-edge. Without these, the command is essentially useless.

* Update lpr.md

* Update pages/common/lpr.md

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

* Update pages/common/lpr.md

Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>
Co-authored-by: marchersimon <50295997+marchersimon@users.noreply.github.com>
Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>

pages/common/lpr.md

@@ -1,8 +1,8 @@
 # lpr
 
 > CUPS tool for printing files.
-> See also `lpstat` and `lpadmin` for listing and configuring printers.
-> More information: <http://www.CUPS.org>.
+> See also: `lpstat` and `lpadmin`.
+> More information: <https://www.cups.org/doc/man-lpr.html>.
 
 - Print a file to the default printer:
 
@@ -22,7 +22,7 @@
 
 - Print double-sided either in portrait (long) or in landscape (short):
 
-`lpr -o sides={{two_sided_long_edge|two_sided_short_edge}} {{path/to/file}}`
+`lpr -o sides={{two-sided-long-edge|two-sided-short-edge}} {{path/to/file}}`
 
 - Set page size (more options may be available depending on setup):