Fix filenames for proposals

[brooksprumo]

Two proposed SIMDs have inconsistent filenames:

• https://github.com/solana-foundation/solana-improvement-documents/blob/main/proposals/simd-0170-builtin-instruction-cost-and-budget.md
• https://github.com/solana-foundation/solana-improvement-documents/blob/main/proposals/simd-0182-conditional-cu-metering.md

Instead, they should be have the "simd-" prefix removed.

[brooksprumo]

@tao-stones - tagging you since these are both your SIMDs

@jacobcreech - tagging you for visibility; maybe theres an automated way to check for this going forward? Or at least can be manually inspected before merging.

[tao-stones]

@tao-stones - tagging you since these are both your SIMDs

Thanks for spotting it, #216 fixes it.