Fix trailing whitespaces

src/librustc/diagnostics.rs

@@ -303,15 +303,15 @@ number cannot be negative.
 E0307: r##"
 The length of an array is part of its type. For this reason, this length must be
 a compile-time constant.
-"##, 
+"##,
 
 E0308: r##"
 This error occurs when the compiler was unable to infer the concrete type of a
 variable. This error can occur for several cases, the most common of which is
 that there is a mismatch in the expected type that the compiler inferred, and
 the actual type that the user defined a variable as.
 
-let a: char = 7;    // An integral type can't be contained in a character, so 
+let a: char = 7;    // An integral type can't be contained in a character, so
                     // there is a mismatch.
 
 let b: u32 = 7;     // Either use the right type...