Update unit tests to newer Swift versions (#270)

Author: Joannis

.github/workflows/main.yml

@@ -16,26 +16,6 @@ jobs:
     strategy:
       matrix:
         include:
-          - xcode: "11.7" # Swift 5.2
-            macOS: "10.15"
-            iOS: "13.7"
-            tvOS: "13.4"
-            useCodecov: "false"
-          - xcode: "12.4" # Swift 5.3
-            macOS: "10.15"
-            iOS: "14.4"
-            tvOS: "14.3"
-            useCodecov: "false"
-          - xcode: "12.5.1" # Swift 5.4
-            macOS: "11.0"
-            iOS: "14.5"
-            tvOS: "14.5"
-            useCodecov: "false"
-          - xcode: "13.1" # Swift 5.5
-            macOS: "11.0"
-            iOS: "15.0"
-            tvOS: "15.0"
-            useCodecov: "false"
           - xcode: "13.4.1" # Swift 5.6
             macOS: "12"
             iOS: "15.5"
@@ -74,12 +54,9 @@ jobs:
     strategy:
       matrix:
         swift:
-          - "5.1"
-          - "5.2"
-          - "5.3"
-          - "5.4"
-          - "5.5"
-          - "5.6"
+          - "5.7"
+          - "5.7"
+          - "5.8"
 
     runs-on: ubuntu-latest
     container:
@@ -93,8 +70,8 @@ jobs:
     strategy:
       matrix:
         swift:
-          - "5.5"
-          - "5.6"
+          - "5.8"
+          - "5.7"
 
     runs-on: windows-2019