calendar width is different to rest of pages

[Chris Hunter]

Describe the bug
the calendar iframe is set to a width of 800, all other pages are 640 wide, should we change the width of the calendar to match the format of the rest of the site or leave it over-hanging the header like it is?

To Reproduce
Steps to reproduce the behavior:

1. Go to https://genomicsstandardsconsortium.github.io/gensc.github.io/pages/calendar.html
2. See error