chore(deps): bump next from 15.5.18 to 15.5.21 in the npm_and_yarn group across 1 directory - #223

Changed pages include:

• index.html - view
• 404.html - view
• community-contracts.html - view
• confidential-contracts.html - view
• contracts-cairo.html - view
• contracts-compact.html - view
• contracts-stylus.html - view
• contracts-sui.html - view
• contracts.html - view
• defender.html - view

There are more changes not included in the list