fix pauses

Author: tshepang

src/doc/rustc-dev-guide/src/tests/ui.md

@@ -320,8 +320,8 @@ be preferred over //@ error-pattern, //@ error-pattern is imprecise and non-exha
 
 ### `error-pattern`
 
-The `error-pattern` [directive](directives.md) can be used for runtime messages, which don't
-have a specific span, or in exceptional cases, for compile time messages.
+The `error-pattern` [directive](directives.md) can be used for runtime messages which don't
+have a specific span, or, in exceptional cases, for compile time messages.
 
 Let's think about this test: