Speed up tests: remove sleep(1000) in resetState (#3869)

Remove the 1s sleep between resetBlocksToSuperflat and clearInventory.
/fill executes synchronously on the server, so the sleep is unnecessary.
Saves ~45s across the full test suite (1s × 45 tests).

Tested locally on 1.9.4: 45/45 passing.

Co-authored-by: rom1504 <rom1504@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rom1504

test/externalTests/plugins/testCommon.js

@@ -91,7 +91,6 @@ function inject (bot) {
     await teleport(new Vec3(0, bot.test.groundY, 0))
     await bot.waitForChunksToLoad()
     await resetBlocksToSuperflat()
-    await sleep(1000)
     await clearInventory()
   }