chore: stop treating dirs as having size 128 (#10750)

Resp. directories for the database, and both dirs and symlinks for
`FileInfo.FileSize`. Instead handle it in the UI progress percentage. We
even already have special cases there for deletions, might as well
handle directories just like any other zero-sized needed item there.

This went through the very thorough testing of running it on my laptop,
the migration was applied and it seemed to be working fine after.

---------

Signed-off-by: Simon Frei <freisim93@gmail.com>

internal/db/sqlite/folderdb_update.go

@@ -111,10 +111,6 @@ func (s *folderDB) Update(device protocol.DeviceID, fs []protocol.FileInfo, opti
 			f.BlocksHash = nil
 		}
 
-		if f.Type == protocol.FileInfoTypeDirectory {
-			f.Size = 128 // synthetic directory size
-		}
-
 		// Insert the file.
 		//
 		// If it is a remote file, set remote_sequence otherwise leave it at