mention setting QT_FONT_DPI in README file since it has no effect in the binary

cmake/packaging/README.macos

@@ -50,7 +50,16 @@ these steps:
 
    lammps-gui ${LAMMPS_BENCH_DIR}/in.rhodo
 
-7. Allow the excutables (lmp, lammps-gui, msi2lmp, binary2txt, phana, stl_bin2txt)
+   Depending on the size and resolution of your screen, the fonts may
+   be too small to read. This can be adjusted by setting the environment
+   variable QT_FONT_DPI. The default value would be 72, so to increase
+   the fonts by a third one can add to the .zprofile file the line
+
+   export QT_FONT_DPI=96
+
+   and reload as shown above.
+
+7. Give permission to execute the commands (lmp, lammps-gui, msi2lmp, binary2txt, phana, stl_bin2txt)
 
    MacOS will likely block the initial run of the executables, since they
    were downloaded from the internet and are missing a known signature from an

tools/lammps-gui/lammpsgui.cpp

@@ -82,7 +82,6 @@ LammpsGui::LammpsGui(QWidget *parent, const char *filename) :
     setWindowIcon(QIcon(":/lammps-icon-128x128.png"));
 #if (__APPLE__)
     QFont text_font("Menlo");
-    setenv("QT_FONT_DPI", "96", 0);
 #else
     QFont text_font(":/Monospace.ttf");
 #endif