Remove bstm gas meter docs as unnecessary

[Eric-Warehime]

Updates the docs to reflect changes in cosmos/cosmos-sdk#26138

[greptile-apps]

Greptile Summary

This PR removes the "Disable the Block Gas Meter" sub-section from the Block-STM parallel execution documentation (sdk/next/experimental/blockstm.mdx), reflecting the upstream change in cosmos/cosmos-sdk#26138 that makes SetDisableBlockGasMeter unnecessary (or no longer available).

• The removed section described calling bApp.SetDisableBlockGasMeter(true) as a prerequisite for parallel execution; this is no longer required.
• The surrounding documentation (Virtual Fee Collection, Object Store setup, Custom Modules) remains intact and reads coherently without the deleted section.
• No internal links or cross-references within the file point to the removed heading.
• References to blockGasMeter found elsewhere in the repo are in versioned SDK docs (v0.47, v0.50, v0.53) that document the general gas-meter feature and are unrelated to this Block-STM-specific removal.

Confidence Score: 5/5

• This is a safe, minimal docs-only change with no code or logic impact.
• The PR removes a single, self-contained documentation section. The change is well-motivated (upstream SDK API removal), the file reads correctly after the deletion, and no other files in the repository reference this specific heading.
• No files require special attention.

Important Files Changed

Filename	Overview
sdk/next/experimental/blockstm.mdx	Removes the "Disable the Block Gas Meter" section (8 lines) from the Block-STM integration guide; the surrounding content remains coherent and no internal links are broken.

_{Last reviewed commit: "Remove bstm gas mete..."}

[evanorti]

LGTM!

Merge away