qemu-doc: Option -ignore-environment removed.

Has been removed in commit fc9c541.

Signed-off-by: Thomas Schwinge <thomas@codesourcery.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

qemu-doc.texi

@@ -2683,9 +2683,6 @@ Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
 Set the x86 stack size in bytes (default=524288)
 @item -cpu model
 Select CPU model (-cpu help for list and additional feature selection)
-@item -ignore-environment
-Start with an empty environment. Without this option,
-the initial environment is a copy of the caller's environment.
 @item -E @var{var}=@var{value}
 Set environment @var{var} to @var{value}.
 @item -U @var{var}