Fix referenes in docs (#39828)

https://dart.googlesource.com/external/github.com/flutter/engine/+/8496df6102d5391116787a95dfd28be64716d232

DEPS

diff --git a/DEPS b/DEPS
index e8518d1..efadf24 100644
--- a/DEPS
+++ b/DEPS
@@ -242,7 +242,7 @@
 deps = {
   'engine/src': 'https://github.com/flutter/buildroot.git' + '@' + '64b0c3deecaff8e66c2deb74e2171e8297b2bfcd',
 
-  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '6a7ea36c89aed08c0437ce708815c3d245412838',
+  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '8496df6102d5391116787a95dfd28be64716d232',
 
   'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'cef1fab3837fc924997585decb67199b406dc30e',
 

commits.json

diff --git a/commits.json b/commits.json
index bd52927..463b827 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "engine/src/flutter":"6a7ea36c89aed08c0437ce708815c3d245412838",
+  "engine/src/flutter":"8496df6102d5391116787a95dfd28be64716d232",
   "engine/src/third_party/dart":"cef1fab3837fc924997585decb67199b406dc30e",
   "flutter":"1c753635b14036dae99488ce30404a1c61a5c71d"
 }
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