docs: Improve Remix IDE connection guide accuracy and user navigation

[medwinfin]

What changed

• Updated the "Deploy & Run Transactions" tab icon description to match current Remix UI (replaced "≡" with actual deployment arrow ▶️)
• Enhanced the Injected Provider selection instructions with detailed step-by-step guidance
• Added missing steps for finding and selecting the provider in Environment Explorer

Why these changes matter

These updates make the documentation more accurate and user-friendly by:

• Eliminating confusion caused by outdated UI references
• Providing clear path for users who don't immediately see Injected Provider option
• Reducing potential support tickets and user frustration during setup

Testing done

• Verified all UI element names and paths in latest Remix IDE version
• Confirmed steps work with different wallet providers (MetaMask, Rabby)
• Validated that instructions match exact UI text and sequence

Screenshots

Before:

After:

[inkjesse]

@medwinfin thank you for your contribution!