Replace "dramatically" with "considerably" in JIT section

Keep language plain and academic per jstac review.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Chihiro2000GitHub

lectures/numba.md

@@ -492,7 +492,7 @@ with qe.Timer():
 ```
 
 If we switch off JIT compilation by removing `@jit`, the code takes
-dramatically longer on our machine.
+considerably longer on our machine.
 
 So we get a large speed gain by adding four characters.