Fix encounter rates for Elekid and Magby in Diamond/Pearl

[Michy1212]

Change description

This PR fixes the encounter rarity values for Elekid (#239) and Magby (#240) in Pokémon Diamond and Pearl (version IDs 12 and 13).

Problem

Both Pokémon currently use encounter slots 9 and 10 (encounter_slots.csv), which have a rarity of 4% each. These slots are shared with Buizel (#418) and Shellos (#422) in the affected areas, so modifying them directly would have incorrectly changed the encounter rates of those Pokémon as well.

Solution

Four dedicated encounter slots were added to encounter_slots.csv with a rarity of 8%:

• 9001 (slot 13) and 9002 (slot 14) for Elekid
• 9003 (slot 15) and 9004 (slot 16) for Magby

The corresponding rows in encounters.csv were updated to point to these new slots:

• Elekid: location areas 8 (Sinnoh Route 205) and 146 (Valley Windworks), for versions 12 and 13 — 8 rows total.
• Magby: location areas 57 (Stark Mountain, exterior), 59 (Stark Mountain, inside) and 174 (Sinnoh Route 227), for versions 12 and 13 — 12 rows total.

Sources

• Bulbapedia: Sinnoh Route 205 — Pokémon Diamond and Pearl
• Bulbapedia: Stark Mountain — Pokémon Diamond and Pearl
• Serebii: Pokémon Diamond/Pearl — Route 205

Contributor check list

• I have written a description of the contribution and explained its motivation.
• I have written tests for my code changes (if applicable).
• I have read and understood the AI Assisted Contribution guidelines.
• I will own this change in production, and I am prepared to fix any bugs caused by my code change.