Fix indentation in tox.ini

Previously, a tab was used to indent a line with a block of code which
otherwise uses eight spaces, causing it to display strangely in text
editors which do not have tabstop=8 set.

TrivialFix

Change-Id: I99a432373beebac912df88e6685db26e738bf654

tox.ini

@@ -9,7 +9,7 @@ install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
          OS_STDOUT_NOCAPTURE=False
          OS_STDERR_NOCAPTURE=False
-	 PYTHONHASHSEED=0
+         PYTHONHASHSEED=0
 
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt