remove pending transaction count

[ayrat555]

Part of #1612

Most of the time pending transaction query won't even start to execute because the request is timeout out on Chain.pending_transaction_count() query. Moreover, it looks like pending_transaction_count variable is not used

Changelog

• remove pending transaction count

[coveralls]

Pull Request Test Coverage Report for Build 75f57044-a9e0-4d12-b9a2-6b03c5175af4

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 9 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.1%) to 80.715%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/fetcher/token.ex	1	78.57%
apps/indexer/lib/indexer/fetcher/token_balance.ex	2	87.1%
apps/indexer/lib/indexer/fetcher/internal_transaction.ex	3	58.62%
apps/indexer/lib/indexer/block/fetcher.ex	3	88.0%

Totals
Change from base Build 2e95c516-1e18-48e1-90e9-f00ed0466d7a:	-0.1%
Covered Lines:	4901
Relevant Lines:	6072

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💛 - Coveralls