package/environment-setup: fix spelling of the script file in the manual.

The manual incorrectly refers to the script file as `setup-environment';
it is actually called `environment-setup'.

Signed-off-by: Konrad Schwarz <konrad.schwarz@siemens.com>
Reviewed-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 7197b1bc44395cbe927dc56f0b7fc53d8ce07636)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/using-buildroot-toolchain.txt

@@ -35,7 +35,7 @@ generating a tarball.
 
 For your convenience, by selecting the option
 +BR2_PACKAGE_HOST_ENVIRONMENT_SETUP+, you can get a
-+setup-environment+ script installed in +output/host/+ and therefore
++environment-setup+ script installed in +output/host/+ and therefore
 in your SDK.  This script can be sourced with
 +. your/sdk/path/environment-setup+ to export a number of environment
 variables that will help cross-compile your projects using the