Removing last column marks first column as non-header

[pomek]

Is this a bug report or feature request? (choose one)

🐞 Bug report

💻 Version of CKEditor

Master

📋 Steps to reproduce

1. Paste the table below somewhere in the editor

	A	B	C
A	X	0-0	0-0
B	0-0	X	0-0
C	0-0	0-0	X

2. Mark first row and first column as Header Row/Column
3. Select first row, last column.
4. Remove the entire column.

✅ Expected result

The first column shouldn't be touched.

❎ Actual result

The first column isn't marked as Header column.

[pomek]

If two columns are headers, the first one stays as a header, the second one loses the attribute when removing the last column.

[jodator]

Probably the same case as here: https://github.com/ckeditor/ckeditor5-table/issues/203. So those should be fixed together.

[scofalik]

DUP https://github.com/ckeditor/ckeditor5-table/issues/203