Fix name of some containers.

Author: grafikrobot

.github/workflows/ci.yml

@@ -34,31 +34,31 @@ jobs:
             install: g++-6
           - toolset: gcc-7
             cxxstd: "11,14,17"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: g++-7
           - toolset: gcc-8
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: g++-8
           - toolset: gcc-9
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
           - toolset: gcc-10
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: g++-10
           - toolset: gcc-11
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: g++-11
           - toolset: gcc-12
             cxxstd: "11,14,17,20,2b"
-            container: ubuntu-22.04
+            container: ubuntu:22.04
             os: ubuntu-latest
             install: g++-12
           - toolset: gcc-13
@@ -87,43 +87,43 @@ jobs:
           - toolset: clang
             compiler: clang++-6.0
             cxxstd: "11,14,17"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-6.0
           - toolset: clang
             compiler: clang++-7
             cxxstd: "11,14,17"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-7
           - toolset: clang
             compiler: clang++-8
             cxxstd: "11,14,17"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-8
           - toolset: clang
             compiler: clang++-9
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-9
           - toolset: clang
             compiler: clang++-10
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-10
           - toolset: clang
             compiler: clang++-11
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-11
           - toolset: clang
             compiler: clang++-12
             cxxstd: "11,14,17,2a"
-            container: ubuntu-20.04
+            container: ubuntu:20.04
             os: ubuntu-latest
             install: clang-12
           - toolset: clang