Update test_example.sh

- Remove BOM
- Fix shebang
- Do not run `cargo check` in parallel
  - `rustc` is good at utilizating cores by default
  - running `cargo check` in parallel messes up the output

examples/test_examples.sh

@@ -1,9 +1,9 @@
-##!/bin/sh
+#!/bin/sh
 
 for example in */; do
 	echo Testing $example...
 	cd $example
-	cargo check &
+	cargo check
 	cd ..
 done