rtw88: remove more references to rtw88fw

When I removed the Realtek rtww8x firmware from base I missed to
add rtw88fw.4 to ObsoleteFiles.inc [1].
While adding this, also remove a leftover reference in rtw88.4.

Reported by:	Herbert J. Skuhra (herbert gojira.at) [1]
Fixes:		cf94672363
MFC after:	3 days

share/man/man4/rtw88.4

@@ -1,9 +1,9 @@
 .\"-
 .\" SPDX-License-Identifier: BSD-2-Clause
 .\"
-.\" Copyright (c) 2022-2025 Bjoern A. Zeeb
+.\" Copyright (c) 2022-2026 Bjoern A. Zeeb
 .\"
-.Dd June 13, 2025
+.Dd February 10, 2026
 .Dt RTW88 4
 .Os
 .Sh NAME
@@ -84,7 +84,6 @@ for network buffer memory to the lower 32bit of physical memory and
 make the driver work.
 .El
 .Sh SEE ALSO
-.Xr rtw88fw 4 ,
 .Xr wlan 4 ,
 .Xr networking 7 ,
 .Xr fwget 8 ,