Replace misplaced string VMware with VirtualBox

In the case of vbfs the host is VirtualBox so mentions of VMware must be
copy-paste errors.

closes #264

Change-Id: Ieb1316155be8f8fb81e3e5a2b21147594f6cb4d9

minix/fs/vbfs/vbfs.8

@@ -12,7 +12,7 @@ host file system when MINIX is run as a VirtualBox guest.
 The above mount command will mount the vbfs file system onto the directory
 \fImountpoint\fR. The \fB\-r\fR mount option makes the file system read-only;
 note that shared folders may independently have been configured as read-only
-on the VMware host. The \fIoptions\fR field is a string consisting of
+on the VirtualBox host. The \fIoptions\fR field is a string consisting of
 comma-delimited \fIkey\fR or \fIkey\fB=\fIvalue\fR options.
 The vbfs server can mount only one shared folder at a time, and therefore,
 specifying a \fBshare\fR name is required.