Fixup header levels

doc/src/Modify.txt

@@ -14,7 +14,7 @@ Section"_Errors.html :c
 
 :line
 
-Modify & extend LAMMPS :h3
+Modify & extend LAMMPS :h2
 
 LAMMPS is designed in a modular fashion so as to be easy to modify and
 extend with new functionality.  In fact, about 95% of its source code

doc/src/Modify_dump.txt

@@ -7,7 +7,7 @@ Documentation"_ld - "LAMMPS Commands"_lc :c
 
 :line
 
-Dump styles :h2
+Dump styles :h3
 
 Classes that dump per-atom info to files are derived from the Dump
 class.  To dump new quantities or in a new format, a new derived dump