.azurepipelines: Use Fedora 43 image for Linux jobs

With the fixes for the C23 standard we can use gcc 15 and
swich over to the latest Fedora image to run the Linux based CI jobs.

Signed-off-by: Oliver Steffen <[email protected]>

Author: osteffenrh

.azurepipelines/templates/defaults.yml

@@ -9,4 +9,4 @@
 
 variables:
   default_python_version: "3.12"
-  default_linux_image: "ghcr.io/tianocore/containers/fedora-41-test:4dbfa9e"
+  default_linux_image: "ghcr.io/tianocore/containers/fedora-43-test:bde74f8"