Fix stuck label and value for uncle block height

[vbaranov]

Fixes #2681

Changelog

Update block view template

Checklist for your PR

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so if necessary
• If I added/changed/removed ENV var, I should update the list of env vars in https://github.com/poanetwork/blockscout/blob/master/docs/env-variables.md to reflect changes in the table here https://poanetwork.github.io/blockscout/#/env-variables?id=blockscout-env-variables. I've set master in the Version column.
• If I add new indices into DB, I checked, that they don't redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build 0e69ef64-2519-4a82-a643-82048a0be588

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.4%) to 78.202%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/fetcher/token.ex	1	80.0%
apps/indexer/lib/indexer/fetcher/token_balance.ex	2	87.88%
apps/indexer/lib/indexer/block/fetcher.ex	3	88.46%

Totals
Change from base Build 3ab17ab2-0f53-4338-9370-0bb6ceb6fcaa:	-0.4%
Covered Lines:	18451
Relevant Lines:	23594

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💛 - Coveralls