fix(docs): remove .mdx extension from signInWithEthereum link in wallet_connect reference

[ygd58]

Closes #1311.

The link to signInWithEthereum in wallet_connect.mdx included a .mdx extension which returns 404.

• ❌ /base-account/reference/core/capabilities/signInWithEthereum.mdx → 404
• ✅ /base-account/reference/core/capabilities/signInWithEthereum → 200

Affected file: docs/base-account/reference/core/provider-rpc-methods/wallet_connect.mdx line 193

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[ygd58]

@roethke @soheimam Could you please review this PR? Found a broken link — signInWithEthereum link had a .mdx extension causing 404. Single file, single line fix. Thanks!