some minor tweaks;

src/lib/libc/hash/SHA256Init.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: SHA256Init.3,v 1.2 2019/12/04 18:28:38 deraadt Exp $
+.\"	$OpenBSD: SHA256Init.3,v 1.3 2019/12/04 19:01:49 jmc Exp $
 .\"
 .\" Copyright (c) 2003, 2004 Todd C. Miller <millert@openbsd.org>
 .\"
@@ -175,9 +175,8 @@ than 2^64 bits as input.
 The SHA-384 and SHA-512 functions can process a message of at most 2^128 - 1
 bits as input.
 .Pp
-The SHA2 functions are considered to be more secure than the
-.Xr sha1 3
-functions with which they share a similar interface.
+The SHA2 functions are considered to be more secure than the SHA1 functions,
+with which they share a similar interface.
 The 224, 256, 384, and 512-bit versions of SHA2 share the same interface.
 SHA512/256, a truncated version of SHA512, is also supported.
 For brevity, only the 256-bit variants are described below.
@@ -230,9 +229,8 @@ The
 .Fn SHA256End
 function is a front end for
 .Fn SHA256Final
-which converts the digest into an
-.Tn ASCII
-representation of the digest in hexadecimal.
+which converts the digest into an ASCII representation
+of the digest in hexadecimal.
 .Pp
 The
 .Fn SHA256File