Could the ages of globular clusters be used to place a limit on the maximum value of the Hubble constant?
No,because a globular cluster has nothing to do with the Hubble Constant.
The Hubble constant describes the expansion of the Universe. The Hubble Constant was revealed when Edwin hubble found a correlation between the distance of a galaxy and its velocity. He found a correlation that was also proportional.
He was talking specifically about galaxies because these are moving away from us and though the expansion of the universe affects all matter it is highly unlikely that the globular clusters would change anything. However it could make the valur of the Hubble constant more accurate.