Use {removeBreakpoint} instead of {toggleBreakpoint} in a web test

This should prevent flakiness even further once asynchronous source
mapping lands.

R=petermarshall@chromium.org

Bug: chromium:1032016
Change-Id: I65797584b8ab539d61421e06928cb4b6780823ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2037991
Commit-Queue: Simon Zünd <szuend@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Auto-Submit: Simon Zünd <szuend@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738500}

third_party/blink/web_tests/http/tests/devtools/sources/debugger/source-frame-breakpoint-decorations.js

@@ -58,11 +58,10 @@
 
       function removeBreakpoint() {
         TestRunner.addResult('Toggle breakpoint');
+        SourcesTestRunner.removeBreakpoint(javaScriptSourceFrame, 2);
         SourcesTestRunner
             .runActionAndWaitForExactBreakpointDecorations(
-                javaScriptSourceFrame, [],
-                () => SourcesTestRunner.toggleBreakpoint(
-                    javaScriptSourceFrame, 2))
+                javaScriptSourceFrame, [], () => {}, true)
             .then(next);
       }
     },