[explorer] Fix ordering of paginated txs

Summary:
In a block containing more txs than the max number of rows, the navigated page is off by one.
This is due to the DataTable() structure that uses a 0-based index despite the query uses a "non-dev human" (aka 1-based) index.

Test Plan: Run the explorer locally and open page for block 000000000000000010f98603f06c377d7148a34806343ac3d7fa9e4346556ce3. Check the tx pagination works as expected.

Reviewers: #bitcoin_abc, tobias_ruck

Reviewed By: #bitcoin_abc, tobias_ruck

Subscribers: tobias_ruck

Differential Revision: https://reviews.bitcoinabc.org/D14375