Reduce the number of make help entries

We've added some more things recently. It seems not worth having almost
the same two entries there anymore.

common.mk

@@ -1503,14 +1503,12 @@ help: PHONY
 	"  test:                ruby core tests" \
 	"  test-all:            all ruby tests [TESTOPTS=-j4 TESTS=<test files>]" \
 	"  test-spec:           run the Ruby spec suite [SPECOPTS=<specs, opts>]" \
-	"  test-rubyspec:       same as test-spec" \
 	"  test-bundler:        run the Bundler spec" \
 	"  test-bundled-gems:   run the test suite of bundled gems" \
 	"  sync-default-gems:   sync default gems from upstream [GEM=<gem_name>]" \
 	"  up:                  update local copy and autogenerated files" \
 	"  benchmark:           benchmark this ruby and COMPARE_RUBY." \
 	"  gcbench:             gc benchmark [GCBENCH_ITEM=<item_name>]" \
-	"  gcbench-rdoc:        gc benchmark with GCBENCH_ITEM=rdoc" \
 	"  install:             install all ruby distributions" \
 	"  install-nodoc:       install without rdoc" \
 	"  install-cross:       install cross compiling stuff" \