fix: MSE→RMSE terminology consistency and classification report table alignment

[Copilot]

Two doc correctness fixes in response to review thread comments on PR #951.

Changes

2-Regression/3-Linear/README.md

• Updated prose from "mean square error (MSE)" → "root mean square error (RMSE)" with corrected definition ("root of the mean…")
• Renamed variable mse → rmse; updated print label from 'Mean error:' → 'RMSE:'

# Before
mse = np.sqrt(mean_squared_error(y_test, pred))
print(f'Mean error: {mse:3.3} ({mse/np.mean(pred)*100:3.3}%)')

# After
rmse = np.sqrt(mean_squared_error(y_test, pred))
print(f'RMSE: {rmse:3.3} ({rmse/np.mean(pred)*100:3.3}%)')

4-Classification/2-Classifiers-1/README.md

• Fixed accuracy row column alignment in classification report table — values were under precision/recall; moved to f1-score/support to match actual sklearn.classification_report() output

	precision	recall	f1-score	support
accuracy	0.80	1199	0.80	1199