Reduce some CI timeouts (#169512)

- `Linux docs_test`: Has been running consistently under 25m, while
timeout was set at 90m.
- `Linux coverage`: Has been running consistently under 1.2h (~75m),
while timeout was set at 120m.
https://dart.googlesource.com/external/github.com/flutter/flutter/+/8b18dde77fa59ba7f87540c05d1aba787198e77a

DEPS

diff --git a/DEPS b/DEPS
index 0924d05..deeebf7 100644
--- a/DEPS
+++ b/DEPS
@@ -14,7 +14,7 @@
   'flutter_git': 'https://flutter.googlesource.com',
   'skia_git': 'https://skia.googlesource.com',
   'llvm_git': 'https://llvm.googlesource.com',
-  'skia_revision': 'cc7963935d9dd21630a15ef9d387296db936ef03',
+  'skia_revision': '274d78ef26665c0d31efb4730629338d709a7e8d',
 
   # WARNING: DO NOT EDIT canvaskit_cipd_instance MANUALLY
   # See `lib/web_ui/README.md` for how to roll CanvasKit to a new version.
@@ -237,7 +237,7 @@
 deps = {
   'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'b414df224a0c41f820103b33a9f0e48ecca9fd5f',
 
-  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '9c89a8fff9e6eb0a1065f99dafeb1c8a172a4d16',
+  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '8b18dde77fa59ba7f87540c05d1aba787198e77a',
 
   'flutter/engine/src/flutter/third_party/depot_tools':
   Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + '580b4ff3f5cd0dcaa2eacda28cefe0f45320e8f7',

commits.json

diff --git a/commits.json b/commits.json
index efb8f7b..909899a 100644
--- a/commits.json
+++ b/commits.json
@@ -1,4 +1,4 @@
 {
-  "flutter":"9c89a8fff9e6eb0a1065f99dafeb1c8a172a4d16",
+  "flutter":"8b18dde77fa59ba7f87540c05d1aba787198e77a",
   "flutter/engine/src/flutter/third_party/dart":"b414df224a0c41f820103b33a9f0e48ecca9fd5f"
 }
\ No newline at end of file