S7 Elephant Configurator fixes (qmk#4614)

* S7 Elephant: Configurator bugfix, part 1

Reformatted the JSON so each key is on its own line:

This makes the keys easier to rearrange.

* S7 Elephant: Configurator bugfix, part 2

Deleted the extra key from LAYOUT_iso_1u:

JSON contents stated this layout used a split Backspace, but the matrix is configured and intended to have a 2u Backspace.

Extended the Backspace to 2u width and deleted the extra key. (This fixes the error that broke LAYOUT_iso_1u's rendering in the Configurator.)

* S7 Elephant: Configurator bugfix, part 3

Fix ISO layouts:

Noticed JSON object for Enter on ISO layouts was immediately after Right Bracket. Inspection of s7_elephant.h revealed the expected and appropriate location to be after ISO Hash.

Moved Enter key to the proper location on all ISO layouts.