Temporarily disable test for devtools-frontend

This cl prepares for crrev.com/c/1934213

Bug: chromium:1016772
Change-Id: I3ed38174fce88373bb205a2e0fc3a63f8d7901cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1936491
Commit-Queue: Jan Scheffler <janscheffler@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720187}

third_party/blink/web_tests/TestExpectations

@@ -5894,3 +5894,6 @@ crbug.com/1006759 http/tests/devtools/editor/php-highlighter.js [ Pass Failure ]
 # Disabled for three-way merge after https://crrev.com/c/devtools/devtools-frontend/+/1934218 is submitted
 crbug.com/1006759 http/tests/devtools/modules-load-network.js [ Pass Failure ]
 crbug.com/1006759 http/tests/devtools/modules-load-source.js [ Pass Failure ]
+
+# Temporary suppression to allow devtools-frontend changes
+crbug.com/1016772 http/tests/devtools/sourcemap-section-warning.js [ Pass Failure ]