update build agents

Author: KodrAus

.github/workflows/ci.yml

@@ -22,24 +22,24 @@ jobs:
     strategy:
       matrix:
         exclude:
-        - os: macos-10.15
+        - os: macos-latest
           rust_target: x86_64-gnu
-        - os: macos-10.15
+        - os: macos-latest
           rust_target: x86_64-msvc
-        - os: windows-2019
+        - os: windows-latest
           rust_target: x86_64-apple-darwin
-        - os: ubuntu-20.04
+        - os: ubuntu-latest
           rust_target: x86_64-msvc
-        - os: ubuntu-20.04
+        - os: ubuntu-latest
           rust_target: x86_64-apple-darwin
         channel:
         - stable
         - beta
         - nightly
         os:
-        - macos-10.15
-        - ubuntu-20.04
-        - windows-2019
+        - macos-latest
+        - ubuntu-latest
+        - windows-latest
         rust_target:
         - x86_64-gnu
         - x86_64-msvc
@@ -69,7 +69,7 @@ jobs:
 
   stable:
     name: "Tests / Stable"
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab
@@ -79,7 +79,7 @@ jobs:
 
   msrv:
     name: "Tests / MSRV"
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab