CI - migrate to docker compose v2

Recent GHA runner images require docker-compose v2.

Ref: actions/runner-images#9557

Author: pavoljuhas

.github/workflows/dockertest.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Checkout submodules
         run: git submodule update --init --recursive
       - name: Build Docker images
-        run: docker-compose build
+        run: docker compose build
       - name: Run C++ tests
         run: docker run --rm qsim-cxx-tests:latest
       - name: Run Python tests
@@ -34,4 +34,4 @@ jobs:
       - name: Test install process
         run: |
           cd install/tests
-          docker-compose up --build
+          docker compose up --build

docs/docker.md

@@ -19,10 +19,10 @@ git submodule update --init --recursive
 To build qsim and run all the tests:
 
 ```
-# docker-compose up --build
+# docker compose up --build
 ```
 
-`docker-compose` will create the `qsim`, `qsim-cxx-tests`, and `qsim-py-tests`
+`docker compose` will create the `qsim`, `qsim-cxx-tests`, and `qsim-py-tests`
 images and automatically run all tests. A successful run should have the
 following messages somewhere in the logs:
 
@@ -34,7 +34,7 @@ qsim-py-tests exited with code 0
 To build without running tests, simply run:
 
 ```
-# docker-compose build
+# docker compose build
 ```
 
 ## Run Simulations