chore: update Yamato images and stop testing against il2cpp on Unity 2020.x (#491)

* update Yamato images
* stop testing against il2cpp

Author: sindharta-tanuwijaya

.yamato/StreamingImageSequence.metafile

@@ -4,19 +4,19 @@ platforms:
   - platform_type: &platform_win
       name: win
       type: Unity::VM
-      image: package-ci/win10:v1.20.1
+      image: package-ci/win10:v4
       flavor: b1.medium
       cmd_prefix: 
   - platform_type: &platform_mac
       name: mac
       type: Unity::VM::osx
-      image: package-ci/mac:v1.20.0-1079282
+      image: package-ci/macos-13:v4
       flavor: m1.mac
       cmd_prefix: 
   - platform_type: &platform_linux
       name: linux
       type: Unity::VM
-      image: package-ci/ubuntu:v3.6.0
+      image: package-ci/ubuntu-20.04:v4
       flavor: b1.medium
       cmd_prefix: DISPLAY=:0.0
 
@@ -54,11 +54,11 @@ test_configs:
   - editor_version: 2020.3
     test_platforms:
       - platform_type: *platform_win
-        test_type: *upm_ci_all
+        test_type: *upm_ci_mono
       - platform_type: *platform_mac
-        test_type: *upm_ci_all
+        test_type: *upm_ci_mono
       - platform_type: *platform_linux
-        test_type: *upm_ci_all
+        test_type: *upm_ci_mono
   - editor_version: 2021.3  
     test_platforms:
       - platform_type: *platform_win