Roll Flutter from 637e5bce662f to 59d26c481acc (17 revisions) (#6599)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index cb8fe40..4362c02 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-637e5bce662fb43459d409e13ba5a7fb2c3fa930
+59d26c481acca4e5b086dc6502b45ca31b273c25