bug#45915: 28.2; delete-char deletes two letters

[Tak Kunihiro]

> One other possibility is to use a slightly different :relative-width
> factor for the two spaces in a table cell: one with the value of 1,
> the other with 1.001 (say).  They will be indistinguishable on
> display, but since the values are not equal, both stretch gfyphs will
> be displayed, not just one.

Function (org-table--align-field) in org-table.el sandwiches 
text by org-table-separator-space as shown below.

    (concat org-table-separator-space
            prefix
            field
            suffix
-           org-table-separator-space)))
+           (propertize org-table-separator-space 'display '(space 
:relative-width 1.001)))))

I confirmed that this modification works good.

>> I have an impression that default characters on
>> org-table-separator-space is problematic.
>
> What do you mean by "default characters"?

Let me take the statement back.