update documentation regarding "integrations button"

[HarHarLinks]

matrix-dimension/docs/installing.md

Line 147 in 08bd131

After configuring Element, click the integrations button (4 squares in the top right of any room) and

4 squares are only shown when there already are widgets.

matrix-dimension/web/app/home/home.component.html

Line 241 in 7be069b

{{'If everything is set up correctly, you\'ll be able to access the admin area of Dimension by clicking the 3x3 grid in the top right of any room in Element. The gear icon' | translate}}

3x3 I can't find at all.

[TheTimeWalker]

Duplicate of #436

[HarHarLinks]

yes, but note there's a place this is referenced that isn't in 436.