[FIX] sap.m.Image: Test page adjusted
[FIX] sap.m.Image: Test page adjusted

Test page was corrected in such a way, that it could fully
follow the accessibility guidelines.

This includes:

- alts provided for all images

BCP: 1880228239

Change-Id: Ic2d1b99c017d374a47b161af338c49bdf616cdb5

SAP/openui5,cschuff/openui5,SAP/openui5,cschuff/openui5,SAP/openui5,SAP/openui5,cschuff/openui5