Bug#897971: gnucash: new upstream version (2.6.21)

[Heinz Repp]

package: gnucash
package: gnucash-common
package: python3-gnucash
version: 2.6.19-1
severity: wishlist
tags: upstream

This release fixes is announced to be the last of the stable 2.x series.
Please consider uploading!

Thank you

Heinz Repp