remove asciinema upload from update-demos target (#2786)

asciinema.org is unreachable from GitHub Actions runners (Azure)
since June 16, 2026 (asciinema/asciinema-server#479), causing the
daily demo CI job to fail consistently. The upload step is not
essential — the CI job's purpose is to validate that demo recordings
can be generated successfully. Remove the -u flag and update the
target's EXHELP text accordingly.

Co-authored-by: Per G. da Silva <pegoncal@redhat.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

Makefile

@@ -627,11 +627,11 @@ deploy-docs: venv
 
 # The demo script requires to install asciinema with: brew install asciinema to run on mac os envs.
 # Please ensure that all demos are named with the demo name and the suffix -demo-script.sh
-.PHONY: update-demos #EXHELP Update and upload the demos.
+.PHONY: update-demos #EXHELP Validate demo recordings.
 update-demos:
 	@for script in hack/demo/*-demo-script.sh; do \
 	  nm=$$(basename $$script -script.sh); \
-	  ./hack/demo/generate-asciidemo.sh -u -n $$nm $$(basename $$script); \
+	  ./hack/demo/generate-asciidemo.sh -n $$nm $$(basename $$script); \
 	done
 
 include Makefile.venv