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

@@ -219,7 +219,7 @@ $`\begin{align}
 \\
 &\;+\left(\dfrac{\partial B_{\rho}}{\partial z}\;-\;\dfrac{\partial B_z}{\partial \rho}\right)\,overrightarrow{e_{\varphi}}\\
 \\
-&\;+\left(
+&\;+
 \dfrac{1}{\rho}\,\left(\dfrac{\partial (\rho\,B_{\varphi})}{\partial \rho}\;-\;\dfrac{\partial B_{\rho}}{\partial \varphi}\right)
 \,\overrightarrow{e_z}
 \end{align}`$