[Impeller] Remove removal of save layer from clip. (#46113)

Fixes https://github.com/flutter/flutter/issues/134705

The save layer is observable so it isn't safe to optimize out.
https://dart.googlesource.com/external/github.com/flutter/engine/+/991f529c64841a4821971862964ca216f1889a6d

DEPS

diff --git a/DEPS b/DEPS
index abd3788..4facdb7 100644
--- a/DEPS
+++ b/DEPS
@@ -264,7 +264,7 @@
 deps = {
   'engine/src': 'https://github.com/flutter/buildroot.git' + '@' + '9780f253156165c515962f5f0c56235d34617689',
 
-  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '0fbd990dbc839ccb61ee635fba4632be9aa2d36e',
+  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '991f529c64841a4821971862964ca216f1889a6d',
 
   'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'b09ecc45bfc1c4ff9a47a87b411e38925864410f',
 

commits.json

diff --git a/commits.json b/commits.json
index 008d22e..af453c9 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "engine/src/flutter":"0fbd990dbc839ccb61ee635fba4632be9aa2d36e",
+  "engine/src/flutter":"991f529c64841a4821971862964ca216f1889a6d",
   "engine/src/third_party/dart":"b09ecc45bfc1c4ff9a47a87b411e38925864410f",
   "flutter":"b0a90aee17e9554d50f19983948b8e802a8a067e"
 }
\ No newline at end of file