chore: remove dependabot config - #129

Changed pages include:

• index.html - view
• 404.html - view
• 404/index.html - view
• about/index.html - view
• code-of-conduct/index.html - view
• schedule/index.html - view
• speakers/index.html - view
• submit/index.html - view
• topic-tables/index.html - view
• _gatsby/slices/_gatsby-scripts-1.html - view