fix whitespace

Author: MasonProtter

doc/src/manual/modules.md

@@ -172,7 +172,7 @@ julia> using .NiceStuff: nice, DOG, NiceStuff
     Qualifying the names being used as in `using NiceStuff: NiceStuff, nice` is recommended over plain
     `using Foo` for released packages, and other code which is meant to be re-used in the future with
     updated dependencies or future versions of julia.
-    
+
     The reason for this is if another dependency starts to export one of the
     same names as `Foo` the code will error due to an ambiguity in which
     package the name should be taken from. This is especially problematic in