protect underscore characters in filenames

Author: akohlmey

lammps-tutorials.tex

@@ -4299,7 +4299,7 @@ \subsubsection{Installing Linux .flatpak variant}
 
 \subsubsection{Installing the macOS .dmg package}
 
-After downloading the LAMMPS-macOS-multiarch-GUI-29Aug2024_update1.dmg file,
+After downloading the LAMMPS-macOS-multiarch-GUI-29Aug2024\_update1.dmg file,
 double-click on it and then drag the LAMMPS\_GUI app bundle
 into the Applications folder shown in the dialog that opens.  To
 enable command-line access, follow the instructions in the README.txt
@@ -4314,7 +4314,7 @@ \subsubsection{Installing the macOS .dmg package}
 
 \subsubsection{Installing the Windows .exe package}
 
-Download the LAMMPS-Win10-64bit-GUI-29Aug2024_update.exe installer.
+Download the LAMMPS-Win10-64bit-GUI-29Aug2024\_update.exe installer.
 Windows may warn you that the file is from an unknown developer
 and was downloaded from the internet.  This happens because neither the
 installer nor the LAMMPS--GUI application (or any other applications inside)