Fix test --example docs.

As part of #5464 I forgot to update the help text.

Closes #5177

Author: ehuss

src/bin/cargo/commands/test.rs

@@ -21,8 +21,8 @@ pub fn cli() -> App {
             "Test only this package's library",
             "Test only the specified binary",
             "Test all binaries",
-            "Check that the specified examples compile",
-            "Check that all examples compile",
+            "Test only the specified example",
+            "Test all examples",
             "Test only the specified test target",
             "Test all tests",
             "Test only the specified bench target",