[api-major] Remove the SVG back-end (PR 15173 follow-up)

This has been deprecated since version `2.15.349`, which is a year ago.
Removing this will also simplify some upcoming changes, specifically outputting of JavaScript modules in the builds.

test/unit/pdf_spec.js

@@ -40,7 +40,6 @@ import {
   getDocument,
   PDFDataRangeTransport,
   PDFWorker,
-  SVGGraphics,
   version,
 } from "../../src/display/api.js";
 import {
@@ -105,7 +104,6 @@ const expectedAPI = Object.freeze({
   renderTextLayer,
   setLayerDimensions,
   shadow,
-  SVGGraphics,
   UnexpectedResponseException,
   updateTextLayer,
   Util,