Remove svg/animations/smil-syncbase-self-dependency.svg

The test svg/animations/smil-syncbase-self-dependency.svg was added in
[1] but was flaky. In trying to deflake it I discovered the behavior
is currently not testable due to crbug.com/337724. I am removing this
test because it's flaky, not fixable, and was never required for the
original bug in the first place.

[1] http://src.chromium.org/viewvc/blink?view=rev&rev=165498

TBR=schenney
NOTRY=true
BUG=231531

Review URL: https://codereview.chromium.org/145663007

git-svn-id: svn://svn.chromium.org/blink/trunk@165698 bbb929c8-8fbe-4397-9dbb-9b2b20218538