fdo#74573: Delete ranges that are non-empty before pasting from clipboard.

The conditional formatting part is still not working. But other bits
appear to be working now.

Change-Id: Ia8a2cbe57cd2fa9ca9ad46635a91a1d8b99b0e7d
This test now passes. Re-enable it.

Change-Id: I04a499666d1704277c24524f9e7cb827600a47db