Remove debug output from util/test.jam

[pdimov]

This comments out an ECHO statement in util/test.jam, which was probably used for debugging purposes. It results in the output

polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive
polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive
polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive
polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive
polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive
polymorphic_text_archive
polymorphic_text_warchive
polymorphic_binary_archive
polymorphic_xml_archive
polymorphic_xml_warchive

before

Performing configuration checks

    - default address-model    : 64-bit (cached) [1]
    - default architecture     : x86 (cached) [1]
    - symlinks supported       : yes (cached)

on each b2 invocation, which is unnecessary.