Update maths.py

Author: Leoniela

nipype/interfaces/fsl/maths.py

@@ -105,7 +105,7 @@ def _format_arg(self, name, spec, value):
 
 class StdImageInput(MathsInput):
 
-    dimension = traits.Enum("T", "X", "Y", "Z", usedefault=True, argstr="-%sTstd", position=4,
+    dimension = traits.Enum("T", "X", "Y", "Z", usedefault=True, argstr="-%sstd", position=4,
                             desc="dimension to standard deviate across")