Delete trailing spaces.

Author: furon-kuina

src/SUMMARY.md

@@ -428,7 +428,7 @@
     - [Unit testing](testing/unit_testing.md)
     - [Documentation testing](testing/doc_testing.md)
     - [Integration testing](testing/integration_testing.md)
-    - [Dev-dependencies](testing/dev_dependencies.md) 
+    - [Dev-dependencies](testing/dev_dependencies.md)
 -->
 
 - [テスト](testing.md)

src/testing/integration_testing.md

@@ -118,7 +118,7 @@ fn test_add() {
 <!-- 
 Creating the module as `tests/common.rs` also works, but is not recommended
 because the test runner will treat the file as a test crate and try to run tests
-inside it. 
+inside it.
 -->
 モジュールを`tests/common.rs`に記述することも可能ですが、`tests/common.rs`中のテストも自動的に実行されてしまうため非推奨です。