Update SD Ruleset to 0.20.0

What does this MR do?

This MR updates SD Ruleset version to v0.20.0 introducing following changes in Pipeline Secret Detection:

• Added support for 23 new credential types
  • AWS credential types: AWSSecretAccessKey, AWSSessionToken, AWSBedrockShortLivedKey and AWSCognitoIdentityPoolID
  • TailscaleOauthClientSecret
  • TailscaleApiAccessToken
  • TailscalePersonalAuthKey
  • SlackAppConfigurationRefreshToken
  • SlackAppConfigurationToken
  • ShopifyPartnerAPIToken
  • PostmanCollectionAccessKey
  • OpenAiServiceAdminKey
  • OpenAiServiceAccountKey
  • OpenAiProjectKey
  • MapboxSecretApiToken
  • IntercomAppAccessToken
  • GrafanaServiceAccountToken
  • GrafanaCloudAccessPolicyToken
  • FlutterwaveProdEncryptedKey
  • FlutterwaveProdSecretKey
  • FlutterwaveProdPublicKey
  • DropboxAppAccessToken
• Enhanced rule quality and coverage for the following existing rules:
  • anthropic_key
  • AWS Access Key ID rule covering different scenarios
  • Mapbox API token
  • Postman API token
  • open ai token
  • Heroku API Key
• Removed rules:
  • AWSSTSKey: Merged with AWS since they overlap by definition
  • Tailscale key: Redundant
  • Grafana API token: Redundant

What are the relevant issue numbers?

• https://gitlab.com/gitlab-org/gitlab/-/issues/334427+
• Bump secret-detection-rules to version v0.20.0 ... (gitlab-org/gitlab#579077) • Vishwa Bhat • 18.7

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests updated/added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer