Roll Flutter from 39a38b7882fe to 587cf5fa715f (5 revisions) (#6078)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index d7869e0..566ce01 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-39a38b7882fe40436176ebc97e554be11141cc7d
+587cf5fa715fffd95df9a224453f265482bb26f5