Observing Capabilities text update request from Virgo

Looking at the text of the section, @gianluca.gemme and I noticed a couple of sentences that need rephrasing to better represent the Virgo position:

• Right after the timeline picture, it is written: "Virgo plans to join toward the end of June, after commissioning to address a damaged mirror that is limiting the performance." This is not really correct and should become: "Virgo plans to join in fall 2023, after commissioning to address a damaged mirror that is limiting the performance and to further improve sensitivity".

• below the table with the PSD files it is written: "These noise curves correspond to the high ends of the BNS ranges shown in the timeline figure above, with the exception of Virgo in O5, for which it represents the low end." This is a long-standing issue with the naming conventions: for Virgo "high" means actually high PSD, that is low end of the BNS range, and viceversa. So the sentence should be updated as: "These noise curves correspond to the high ends of the BNS ranges shown in the timeline figure above, with the exception of Virgo in O4, for which it represents the low end."

Thanks, Alessio