Apply Layout/SpaceInLambdaLiteral rubocop rule

I had mixed feelings about this rule, since I like spaces where
possible.

However, I changed my mind when I realized writing `->(thing) { }` was
similar to defining a method, and we don't have a space before the
parenthesis when defining a method.

.rubocop.yml

@@ -115,6 +115,9 @@ Layout/SpaceBeforeFirstArg:
 Layout/SpaceBeforeSemicolon:
   Enabled: true
 
+Layout/SpaceInLambdaLiteral:
+  Enabled: true
+
 Layout/SpaceInsideArrayLiteralBrackets:
   Enabled: true