Fix fully-qualified QbFields path in Sphinx nitpicky config

[harryswift01]

Summary

This PR updates the Sphinx nitpicky ignore configuration to use the fully‑qualified import path for a deprecated aiida symbol, fixing a clean-build failure under -nW.

Changes

Fix QbFields reference path in Sphinx config

• Update nitpick_ignore to use aiida.orm.fields.QbFields instead of the unqualified name.
• Prevents first‑run Sphinx failures caused by unresolved autodoc cross‑references.
• Makes documentation builds deterministic under strict (-nW) settings.

Impact

• Stabilises clean documentation builds (including CI).
• No functional impact on runtime code.
• Improves compatibility with newer aiida versions and strict Sphinx configurations.

[coveralls]

Pull Request Test Coverage Report for Build 21207905270

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 81.949%

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Totals
Change from base Build 21207484124:	0.0%
Covered Lines:	1026
Relevant Lines:	1252

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💛 - Coveralls

[jimboid]

Good catch, safe to ignore this because it is inbuilt DFT fields