[INTERNAL] sap.m.MessageBox: add missing commas
[INTERNAL] sap.m.MessageBox: add missing commas

Some of the snippets were missing commas in the API description.

Closes https://github.com/SAP/openui5/pull/2260

Change-Id: I075160b2413975e608fffad914ee56ed709f7292

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