Change gcc12 to gcc11 so that the gcov version matches

Author: cacharle

.github/workflows/ci.yml

@@ -23,8 +23,8 @@ jobs:
           # older libzmq and without draft
           - os: "ubuntu-22.04"
             cppstd: "11"
-            cc: "gcc-12"
-            cxx: "g++-12"
+            cc: "gcc-11"
+            cxx: "g++-11"
             drafts: "OFF"
             libzmq: "4.2.0"
             libzmqbuild: "pkgconfig"
@@ -47,8 +47,8 @@ jobs:
           # coverage (gcc version should match gcov version)
           - os: "ubuntu-22.04"
             cppstd: "17"
-            cc: "gcc-12"
-            cxx: "g++-12"
+            cc: "gcc-11"
+            cxx: "g++-11"
             drafts: "ON"
             curve: "ON"
             libzmq: "4.3.5"