Fix spacing

src/2025-12-19/presentation.tex

@@ -395,7 +395,7 @@
         \begin{gather*}
             X \sim \mathcal{N}\mleft( \mu, \sigma^2 \mright)
         \end{gather*}%
-        \vspace{2mm}
+        \vspace{0mm}
         \begin{align*}
             f_X(x) &= \frac{1}{\sqrt{2\pi \sigma^2}} \exp\left(\frac{(x -
             \mu)^2}{2 \sigma^2} \right) \\[2mm]