Update to official Swift 5.2 release for CI

Author: Mordil

.github/workflows/tests.yml

@@ -23,7 +23,10 @@ jobs:
     steps:
     - uses: actions/checkout@v1
     - name: Check Swift version
-      run: swift --version
+      run: |
+        sudo xcode-select -s /Applications/Xcode_11.3.app/
+        export TOOLCHAINS=swift
+        swift --version
     - name: Run tests
       run: swift test
 
@@ -33,7 +36,7 @@ jobs:
     - uses: actions/checkout@v1
     - name: Check Swift version
       run: |
-        sudo xcode-select -s /Applications/Xcode_11.4_beta.app/
+        sudo xcode-select -s /Applications/Xcode_11.4.app/
         export TOOLCHAINS=swift
         swift --version
     - name: Run tests
@@ -59,7 +62,7 @@ jobs:
 
   ubuntu-bionic-5_2:
     container:
-      image: swiftlang/swift:nightly-5.2-bionic
+      image: swift:5.2-bionic
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1
@@ -96,7 +99,7 @@ jobs:
 
   ubuntu-xenial-5_2:
     container:
-      image: swiftlang/swift:nightly-5.2-xenial
+      image: swift:5.2-xenial
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1