fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Assistant/WebApp/Form.hs

@@ -129,7 +129,7 @@ withExpandableNote field (toggle, note) = withNote field $ [whamlet|
   ^{note}
 |]
   where
-  	ident = "toggle_" ++ toggle
+	ident = "toggle_" ++ toggle
 
 {- Adds a check box to an AForm to control encryption. -}
 #if MIN_VERSION_yesod(1,2,0)