HTML endpoint /inscriptions/block/<height>/<page> returns nothing after page 0

[gmart7t2]

• go to https://ordinals.com/block/800000
• it correctly shows "2914 Inscriptions"
• click "more" -> https://ordinals.com/inscriptions/block/800000
• it correctly shows the first 100 inscriptions
• click "next" -> https://ordinals.com/inscriptions/block/800000/1
• it incorrectly shows no inscriptions

Both Server::inscriptions_in_block_paginated() and InscriptionsBlockHtml::new() are removing the first page_index * page_size inscriptions. Only one of them should do it.

This commit fixes the issue.

[raphjaph]

Thanks!

Just simplified the logic a bit and wrote a test.