[v2-9] Update references to CNCF calendar - #2628

Changed pages include:

• index.html - view
• 404.html - view
• adopters/index.html - view
• blog/index.html - view
• community/index.html - view
• contributing/index.html - view
• ecosystem/index.html - view
• flagger/index.html - view
• flux/index.html - view
• governance/index.html - view

There are more changes not included in the list