Fix unused warning in fields_count.hpp

[anarthal]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 11258716667

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 100.0%

---

Totals
Change from base Build 11253776824:	0.0%
Covered Lines:	407
Relevant Lines:	407

---

💛 - Coveralls

[anarthal]

Would you be open to a PR that changes CIs to use warnings-as-errors=on and warnings=extra so Boost.PFR is ensured to be clean of common warnings for downstream consumers (like me)?

[apolukhin]

warnings-as-errors=on and warnings=extra

Would you be open to a PR that changes CIs to use warnings-as-errors=on and warnings=extra so Boost.PFR is ensured to be clean of common warnings for downstream consumers (like me)?

Sounds good, please make a PR