Update cheatsheet.fr.md

12.temporary_ins/20.magnetostatics-vacuum/40.ampere-theorem-applications/30.cylindrical-current-distributions/10.rectilinear-current/20.ampere-local/20.overview/cheatsheet.fr.md

@@ -215,7 +215,7 @@ $`\begin{align}
 <br>
 $`\begin{align}
 \mathbf{\overrightarrow{rot}\,\overrightarrow{B}}
-&=\left(\dfrac{1}{\rho}\,\dfrac{\partial B_z}{\partial\varphi}\;-\;\dfrac{\partial B_{\varphi}}{\partial z}\right)\,\overrightarrow{e_{\rho}}\\
+&\mathbf{\boldsymbol{=\left(\dfrac{1}{\rho}\,\dfrac{\partial B_z}{\partial\varphi}\;-\;\dfrac{\partial B_{\varphi}}{\partial z}\right)\,\overrightarrow{e_{\rho}}}}\\
 \\
 &\quad +\left(\dfrac{\partial B_{\rho}}{\partial z}\;-\;\dfrac{\partial B_z}{\partial \rho}\right)\,\overrightarrow{e_{\varphi}}\\
 \\