Retag as v3.15.4.1 (no source changes)

Empty commit to obtain a distinct downstream tag for CPaaS packaging
purposes only. Tree is identical to the v3.15.4 CVE-fix build
(commit ce0d26e, HELM-750/HELM-761): same CVE fixes, same Go 1.26
build, same FIPS 140-3 via GODEBUG=fips140=auto.

This gives the RPM package a distinct Version (3.15.4.1) via
git describe --tags, letting it publish to its own mirror path
without needing the RelEng/ETERA config change blocked on
RELENG-362. The embedded 'helm version' string remains v3.15.4,
unchanged, since the source is unchanged.

See: HELM-812

Author: baijum