doc/make_cheatsheet.md: fix typos

doc/make_cheatsheet.md

@@ -36,9 +36,9 @@ $ make check
 It runs (about) three test suites:
 
 * `make test` (a test suite for the interpreter core)
-* `make test-all` : (for all builtin classes and libraries)
-* `make test-spec` : (a conformance test suite for Ruby implementations)
-* `make test-bundler` : (a test suite for the bundler examples)
+* `make test-all` (for all builtin classes and libraries)
+* `make test-spec` (a conformance test suite for Ruby implementations)
+* `make test-bundler` (a test suite for the bundler examples)
 
 ## How to run the test suite with log