Remove unused Create() from core/svg 1/3

As advised in [1], after porting all uses of Foo::Create() to
MakeGarbageCollected<Foo>() in //third_party/blink/renderer/core/svg,
this CL removes the unused factory methods.

[1] https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/iJ1bawbxbWs/vEdfT5QtBgAJ

Bug: 939691
Change-Id: I6a9d7dcc5a4c00497d35987bb91cfef69a95784a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1576564
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653581}
48 files changed