.travis.yml: Update the jobs to Ubuntu 22.04

According to our support policy, we'll soon drop our official support
for Ubuntu 20.04 ("Focal Fossa") in QEMU. Thus we should update the
Travis jobs now to a newer release (Ubuntu 22.04 - "Jammy Jellyfish")
for future testing. Since all jobs are using this release now, we
can drop the entries from the individual jobs and use the global
setting again.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20240418101056.302103-6-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.travis.yml

@@ -1,5 +1,5 @@
 os: linux
-dist: focal
+dist: jammy
 language: c
 compiler:
   - gcc
@@ -7,7 +7,7 @@ cache:
   # There is one cache per branch and compiler version.
   # characteristics of each job are used to identify the cache:
   # - OS name (currently only linux)
-  # - OS distribution (for Linux, bionic or focal)
+  # - OS distribution (e.g. "jammy" for Linux)
   # - Names and values of visible environment variables set in .travis.yml or Settings panel
   timeout: 1200
   ccache: true
@@ -81,7 +81,6 @@ jobs:
 
     - name: "[aarch64] GCC check-tcg"
       arch: arm64
-      dist: focal
       addons:
         apt_packages:
           - libaio-dev
@@ -116,7 +115,6 @@ jobs:
 
     - name: "[ppc64] GCC check-tcg"
       arch: ppc64le
-      dist: focal
       addons:
         apt_packages:
           - libaio-dev
@@ -151,7 +149,6 @@ jobs:
 
     - name: "[s390x] GCC check-tcg"
       arch: s390x
-      dist: focal
       addons:
         apt_packages:
           - libaio-dev
@@ -195,7 +192,6 @@ jobs:
 
     - name: "[s390x] GCC (other-system)"
       arch: s390x
-      dist: focal
       addons:
         apt_packages:
           - libaio-dev
@@ -225,7 +221,6 @@ jobs:
 
     - name: "[s390x] GCC (user)"
       arch: s390x
-      dist: focal
       addons:
         apt_packages:
           - libgcrypt20-dev
@@ -240,8 +235,7 @@ jobs:
 
     - name: "[s390x] Clang (disable-tcg)"
       arch: s390x
-      dist: focal
-      compiler: clang-10
+      compiler: clang
       addons:
         apt_packages:
           - libaio-dev
@@ -267,7 +261,6 @@ jobs:
           - libvdeplug-dev
           - libvte-2.91-dev
           - ninja-build
-          - clang-10
       env:
         - TEST_CMD="make check-unit"
         - CONFIG="--disable-containers --disable-tcg --enable-kvm --disable-tools