ci: fix podman-next test Go version mismatch (knative#3843)

* ci: fix podman-next test Go version mismatch

Fedora 43's Go package (1.25.10) sets GOTOOLCHAIN=local,
which prevents auto-downloading a newer toolchain. Since
go.mod now requires Go 1.26, the Docker build fails at
`go mod download`.

Setting GOTOOLCHAIN=auto lets the installed Go detect the
version requirement and fetch the correct toolchain.

Signed-off-by: Matej Vašek <matejvasek@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>

* ci: bump podman-next Dockerfile to Fedora 44

Fedora 43 ships Go 1.25.10, but go.mod now requires
Go 1.26 after the recent dependency upgrades. Fedora 44
ships Go 1.26, fixing the build failure.

Signed-off-by: Matej Vašek <matejvasek@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>

---------

Signed-off-by: Matej Vašek <matejvasek@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: matejvasek

Dockerfile.podman-next

@@ -1,4 +1,4 @@
-FROM fedora:43
+FROM fedora:44
 
 RUN dnf -y copr enable rhcontainerbot/podman-next && \
     dnf -y install podman socat go make git && \