sekrit: remove -f flag for sekrit_add

Not only it parsed the wrong character 2 commits ago, it's also
completely broken: file can't be overwritten, because of `chmod 400`.

bin/sekrit.1

@@ -10,7 +10,7 @@
 .\" Dedication along with this software. If not, see
 .\" <http://creativecommons.org/publicdomain/zero/1.0/>.
 .\"
-.Dd August 26, 2020
+.Dd December 2, 2020
 .Dt SEKRIT 1
 .Os
 .Sh NAME
@@ -19,7 +19,6 @@
 .Sh SYNOPSIS
 .Nm
 .Cm add
-.Op Fl f
 .Ar key
 .Op Ar value ...
 .Nm
@@ -52,7 +51,7 @@ Because of this,
 can be used as an account credentials manager,
 or as a general-purpose key-value store of encrypted information.
 .Bl -tag -width Ds
-.It Nm Cm add Oo Fl f Oc Ar key Op Ar value ...
+.It Nm Cm add Ar key Op Ar value ...
 Adds a value to
 .Ar key .
 .Ar value
@@ -65,9 +64,7 @@ will read the value from standard input.
 .Cm add
 will fail if
 .Ar key
-already has a value, unless
-.Fl f
-is specified.
+already has a value.
 .It Nm Cm cp Oo Fl k Oc Ar key
 Decrypts the value associated with
 .Ar key