Amend merged revision history after rewrite.

We had to rewrite the history for external/chromium_org after the Blink
merge, so these old merged revision entries refer to commits that no
longer exist. Delete them to avoid confusing the merge script.

Change-Id: I1dc6e53fefb299f79eced7c26ea64bd344a857ab
diff --git a/.merged-revisions b/.merged-revisions
index a5c3f91..e69de29 100644
--- a/.merged-revisions
+++ b/.merged-revisions
@@ -1,2 +0,0 @@
-5821806d5e7f356e8fa4b058a389a808ea183019 8e79a8efe247f109aafd917a69e8a392961b3687 7dfd6543aa839a4b8af91b8f11227821b408c691
-2a99a7e74a7f215066514fe81d2bfa6639d9eddd 61c449bbbb53310a8c041d8cefdd6b01a126cc7e 986b584c85ac43b40d9f280cef5b8329bcbd10e5