feat: remove dropped/replaced transactions in pending transactions list

[zachdaniel]

Resolves: #1488

Motivation

We only want to show truly pending transactions on the pending transactions page.

This also removes the pending transaction behavior for dropped/replaced transaction detail pages.

[coveralls]

Pull Request Test Coverage Report for Build f0bf3385-4d54-4bad-8b2a-bfd5a64258b8

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• 10 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 84.663%

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Files with Coverage Reduction	New Missed Lines	%
apps/block_scout_web/lib/block_scout_web/views/transaction_view.ex	1	93.55%
apps/explorer/lib/explorer/chain.ex	9	90.52%

Totals
Change from base Build 9fd3a554-733b-4ae2-9e07-c44fc41b9489:	0.02%
Covered Lines:	4256
Relevant Lines:	5027

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 7465c95f-0f8e-40bc-bc51-5c67924cfad0

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 84.848%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/pending_transaction/fetcher.ex	1	73.08%

Totals
Change from base Build 5052dc7f-8d63-40eb-a201-7918152f975b:	0.0%
Covered Lines:	4267
Relevant Lines:	5029

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💛 - Coveralls