Remove o-flag as it is redundant

Even if we extend the flag to be an n-flag with a numerical input, we
already have other Unix-tools to take care of us much more flexibly,
e.g. with head(1) you can easily get the first 10 outputs with

	slstatus -s | head -n 10,

but also e.g. discard the first one and then get the consecutive 10
outputs.

For the X11-root-window-name, you can limit the runtime with timeout(1)
or a comparable solution.

This reverts commit fa8b939990.

slstatus.1

@@ -6,7 +6,7 @@
 .Nd suckless status monitor
 .Sh SYNOPSIS
 .Nm
-.Op Fl so
+.Op Fl s
 .Sh DESCRIPTION
 .Nm
 is a suckless status monitor for window managers that use WM_NAME (e.g. dwm) or
@@ -18,8 +18,6 @@ outputs to WM_NAME.
 .Bl -tag -width Ds
 .It Fl s
 Write to stdout instead of WM_NAME.
-.It Fl o
-Write only once and exit.
 .El
 .Sh CUSTOMIZATION
 .Nm

slstatus.c

@@ -42,7 +42,7 @@ difftimespec(struct timespec *res, struct timespec *a, struct timespec *b)
 static void
 usage(void)
 {
-	die("usage: %s [-so]", argv0);
+	die("usage: %s [-s]", argv0);
 }
 
 int
@@ -51,18 +51,15 @@ main(int argc, char *argv[])
 	struct sigaction act;
 	struct timespec start, current, diff, intspec, wait;
 	size_t i, len;
-	int sflag, oflag, ret;
+	int sflag, ret;
 	char status[MAXLEN];
 	const char *res;
 
-	sflag = oflag = 0;
+	sflag = 0;
 	ARGBEGIN {
 		case 's':
 			sflag = 1;
 			break;
-		case 'o':
-			oflag = 1;
-			break;
 		default:
 			usage();
 	} ARGEND
@@ -112,10 +109,6 @@ main(int argc, char *argv[])
 			XFlush(dpy);
 		}
 
-		if (oflag) {
-			done = 1;
-		}
-
 		if (!done) {
 			if (clock_gettime(CLOCK_MONOTONIC, &current) < 0) {
 				die("clock_gettime:");