Turn back on volpiano display for MS 73

[dchiller]

In #1649, we turned off any volpiano display for MS 73 so melody entry could proceed while we determined what to do in cases like these: the chants have been proofread and published so should not be completely unpublished, but newly entered data (ie. the volpiano) should not be shown until proofread.

This issue should basically reverse the changes in #1649.

The following pages were changed and should be checked that they are working for MS 73 chants for this issue to be completed:

• chant detail
• global chant search
• ms chant search
• source chant browse
• source list
• melody search (global and source-specific)