Update python-slack-sdk to version 3.21.3 / rev 7 via SR 1090102
    
    https://build.opensuse.org/request/show/1090102
    by user StevenK + dimstar_suse
    - Update to 3.21.3:
      * #1361 Fix #1356 files_upload_v2 filename required even though content
        provided
      * #1354 Fix a bug where SQLAlchemy based InstallationStore is missing
        client_id in queries
      * #1352 Improve the default OAuth page content renderer not to embed
        external parameters as-is
      * Update Audit Logs API response class to have newly added properties
      * #1349 Add five admin API supports to Web API clients (admin.roles.*,
        admin.conversations.convertToPublic, admin.conversations.lookup)
      * #1345 Add team parameter support to the authorize URL generators
      * #1343 Fix #1342 files_upload_v2 fails to share files in a channel
      * #1334 Fix #1333 Enable using RetryHandler for 200 OK response patterns
      * #1335 Fix #1327 OAuth module: SQLAlchemy v2 compatibility
      * #1