Add M75 to tools/binary_size/generate_milestone_reports.py

Change-Id: I47a48f080f1d9f9e642e1af3debb0b7d3b967cac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1586344
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Commit-Queue: Eric Stevenson <estevenson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654603}

tools/binary_size/generate_milestone_reports.py

@@ -59,7 +59,8 @@ _DESIRED_VERSIONS = [
     '71.0.3578.99',
     '72.0.3626.105',
     '73.0.3683.75',
-    '74.0.3729.11',  # Beta
+    '74.0.3729.112',
+    '75.0.3770.12',  # Beta
 ]