Changed windows runner to specific version, to follow recommended guidelines of specified version

Author: Martin Boje Carpentier

.github/workflows/ci-build.yml

@@ -19,7 +19,7 @@ jobs:
   build:
 
     name: 'Build and Test'
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     env: 
       VSTEST_CONNECTION_TIMEOUT: 900

.github/workflows/continous-benchmark.yml

@@ -6,7 +6,7 @@ on:
 jobs:
   benchmark:
     name: Continuous benchmarking
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     defaults:
       run:

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
   deploy:
     name: 'Deploy to Nuget'
     if: github.event_name == 'release'
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     steps:
       - uses: actions/checkout@v2