Revert "loader.efi(8): Document LoaderEnv and NextLoaderEnv EFI variables"

This reverts commit cf7d4b04e9.

I attributed the wrong author of the patch.

stand/man/loader.efi.8

@@ -217,47 +217,14 @@ functionality where we use the video console if a keyboard is connected and a
 serial console otherwise.
 .Ss Additional Environment Variables
 .Nm
-can set variables early in startup from a file on the EFI partition.
-By default, that file is
-.Pa /efi/freebsd/loader.env .
-It can be changed by setting the FreeBSD EFI variable
-.Va LoaderEnv ,
-as in:
-.Bd -literal -offset indent
-echo -n /efi/freebsd/alt.env | efivar -w -t 7 \\
-    -n cfee69ad-a0de-47a9-93a8-f63106f8ae99-LoaderEnv
-.Ed
-.Pp
-After that is executed, the file
-.Pa /efi/freebsd/alt.env
-is used instead of
-.Pa /efi/freebsd/loader.env .
-See
-.Xr efivar 8
-for more information on setting EFI variables.
-.Pp
-The EFI variable
-.Va NextLoaderEnv
-can be set to the pathname of a second startup file.
-That variable is deleted immediately after its value is retrieved,
-so setting it will affect only the next boot attempt.
-For either variable, a missing file is silently ignored.
-.Pp
-Only simple variables can be set in the startup file.
+loads some extra variables early in startup from
+.Pa /efi/freebsd/loader.env
+from the EFI partition.
+Only simple variables can be set here.
 It can be useful to specify the root filesystem:
 .Bd -literal -offset indent
 rootdev=disk0s1a
 .Ed
-.Pp
-The startup file contains a series of assignments separated by spaces,
-tabs, or newlines.
-Quotes are not given any special treatment.
-If no
-.Li =value
-is given, the value
-.Li 1
-is used.
-Invalid syntax and the like are silently ignored.
 .Ss Staging Slop
 The kernel must parse the firmware memory map tables to know what memory
 it can use.