fix(operator): default fips140 to off via go.mod, not the chart

[nshidlansik]

What does this PR do?

Follow-up to the v0.2 FIPS 140-3 backport (#348): fixes the same bug that
was fixed on main in #349.

fipsMode: off (the chart default) silently ran the operator with FIPS mode
enabled instead of disabled. GOFIPS140=v1.0.0 at build time makes the
operator binary's own compiled-in GODEBUG default fips140=on (per Go's
own docs: GOFIPS140 "enable[s] FIPS 140-3 mode by default", and the
fips140 GODEBUG option "defaults to off unless GOFIPS140 is set at build
time"). deployment.yaml's {{- if ne .Values.fipsMode "off" }} guard
around the GODEBUG env var meant fipsMode=off set no GODEBUG at all, so
the binary fell through to its compiled-in on default: off and on were
identical.

Fix: add a godebug fips140=off directive to operator/go.mod, which
overrides GOFIPS140's default back to off at compile time. The chart's
{{- if ne .Values.fipsMode "off" }} guard is kept as-is.

Verified with crypto/fips140.Enabled() run inside the operator module:

GOFIPS140=v1.0.0, no GODEBUG at runtime -> Enabled() == false (was true before this fix)
GOFIPS140=v1.0.0, GODEBUG=fips140=on    -> Enabled() == true
GOFIPS140=v1.0.0, GODEBUG=fips140=only  -> Enabled() == true

Found by Aviad Hayumi in review after #335 (the main source of the
backport) merged.

Related issue(s)

Relates to #334

Checklist

• All commits are signed off with DCO (git commit -s)
• New/modified files have SPDX license and copyright headers
• Documentation updated (if applicable)
• Tests pass (make check)
• No proprietary or internal information included