Fix whitespace warnings reported by luacheck (#1229)

tests/examples/awful/placement/compose2.lua

@@ -2,7 +2,6 @@ screen[1]._resize {x = 175, width = 128, height = 96} --DOC_NO_USAGE --DOC_HIDE
 local awful = {placement = require("awful.placement")} --DOC_HIDE
 local c = client.gen_fake {x = 220, y = 35, width=40, height=30} --DOC_HIDE
 
-
     -- Simulate Windows 7 "edge snap" (also called aero snap) feature
     local axis = "vertically"
 

tests/examples/text/gears/object/signal.lua

@@ -9,7 +9,7 @@ end
 
 o:connect_signal("my_signal", slot)
 
- -- Emit can be done without argument. In that case, the object will be 
+ -- Emitting can be done without arguments. In that case, the object will be
  -- implicitly added as an argument.
 o:emit_signal "my_signal"
 

tests/examples/wibox/container/rotate/angle.lua

@@ -29,28 +29,24 @@ local normal = create_arrow("Normal")
 
 local north  = wibox.container {
     create_arrow("North"),
- 
     direction = "north",
     widget    = wibox.container.rotate
 }
 
 local south  = wibox.container {
     create_arrow("South"),
- 
     direction = "south",
     widget    = wibox.container.rotate
 }
 
 local east  = wibox.container {
     create_arrow("East"),
- 
     direction = "east",
     widget    = wibox.container.rotate
 }
 
 local west  = wibox.container {
     create_arrow("West"),
- 
     direction = "west",
     widget    = wibox.container.rotate
 }