Delete TestOverloadedConstructors.idl

TestOverloadedConstructors.idl is not needed now that there's the more
comprehensive TestInterfaceConstructor.idl, so delete.

TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/102133009

git-svn-id: svn://svn.chromium.org/blink/trunk@164059 bbb929c8-8fbe-4397-9dbb-9b2b20218538