sysutils/conky{-awesome}: update to 1.21.3

ChangeLog: https://github.com/brndnmtthws/conky/releases/tag/v1.21.3

Bug fixes

• Replace strncat with strcat
• Fix minimum height not being applied
• Revert removal of dpi scaling
• Fix for the graph scale text colour changing depending on graph position
• Restore previous strut behavior

Miscellaneous

• Bump version
• Docker: make sure image has sensible default name
• Docker: only write to cache if creds available
• Docker cache extern pr
• build(deps): bump the actions group with 2 updates