Fix typos

Author: stomar

src/testing/dev_dependencies.md

@@ -1,7 +1,7 @@
 # Development dependencies
 
-Sometimes there is a need to have a dependencies for tests (examples,
-benchmarks) only. Such dependencies are added to `Cargo.toml` in
+Sometimes there is a need to have dependencies for tests (examples,
+benchmarks) only. Such dependencies are added to `Cargo.toml` in the
 `[dev-dependencies]` section. These dependencies are not propagated to other
 packages which depend on this package.