Fix stripcom() description wrt. comments not on their own line

Neither netstart's nor install.sub's (subtly different) implementations
remove trailing comments on lines not starting as a comment, e.g.,
lines like "up #not down" go through unaltered and without "#not down"
being removed.
Only lines *beginning* with the comment sign ("#") are stripped.
No functional change, just updating function descriptions.

src/etc/netstart

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: netstart,v 1.203 2020/05/21 11:54:41 kn Exp $
+#	$OpenBSD: netstart,v 1.204 2020/05/21 13:42:02 kn Exp $
 
 # Turn off Strict Bourne shell mode.
 set +o sh
@@ -11,8 +11,7 @@ usage() {
 	exit 1
 }
 
-# Echo file $1 to stdout. Skip comment lines and delete everything
-# after the first '#' from other lines. Strip leading and trailing
+# Echo file $1 to stdout. Skip comment lines. Strip leading and trailing
 # whitespace if IFS is set.
 # Usage: stripcom /path/to/file
 stripcom() {