Fix display issue

app.py

@@ -430,7 +430,7 @@ def create_gradio_ui():
     
     Pressing "Train Coefficients" aims to solve
     $$
-    \argmin_{\alpha\in\mathbb{R}^m}\|\mathbf{\Phi\alpha-u}\|_2^2,
+    \argmin_{\alpha\in\mathbb{R}^m}\|{\Phi\alpha-u}\|_2^2,
     $$
     where $\Phi$ contains the features depending on the kernel.
     """