Don't use unstable rustfmt options

rustfmt.toml

@@ -1,4 +1,3 @@
-match_block_trailing_comma = true
 max_width = 80
 newline_style = "Unix"
 reorder_imports = true

src/urlencoded/ser/pair.rs

@@ -239,7 +239,7 @@ where
                     key: value.serialize(key_serializer)?,
                 };
                 Ok(())
-            },
+            }
             PairState::WaitingForValue { key } => {
                 let result = {
                     let value_sink = ValueSink::new(self.urlencoder, &key);
@@ -252,7 +252,7 @@ where
                     self.state = PairState::WaitingForValue { key };
                 }
                 result
-            },
+            }
             PairState::Done => Err(Error::done()),
         }
     }