refactor: fix compiler warnings

[scarf005]

Purpose of change (The Why)

those compiler warnings were annoying and kept hiding other important errors

Describe the solution (The How)

do as the compiler says.

Describe alternatives you've considered

Testing

it builds without errors.

Additional context

[121/495] Building CXX object src/CMakeFiles/cataclysm-bn-tiles-common.dir/character.cpp.o
/var/home/scarf/repo/cata/Cataclysm/src/character.cpp:8767:13: warning: unused variable 'rolls' [-Wunused-variable]
 8767 |         int rolls = 4;
      |             ^~~~~
1 warning generated.
[178/495] Building CXX object src/CMakeFiles/cataclysm-bn-tiles-common.dir/game.cpp.o
/var/home/scarf/repo/cata/Cataclysm/src/game.cpp:8537:31: warning: comparison of integers of different signs: 'int' and 'size_type' (aka 'unsigned long') [-Wsign-compare]
 8537 |             for( int i = 0; i < disassembly_stacks_res.size(); i++ ) {
      |                             ~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
[311/495] Building CXX object src/CMakeFiles/cataclysm-bn-tiles-common.dir/recipe.cpp.o
/var/home/scarf/repo/cata/Cataclysm/src/recipe.cpp:605:20: warning: unused function 'dump_requirements' [-Wunused-function]
  605 | static std::string dump_requirements(
      |                    ^~~~~~~~~~~~~~~~~
1 warning generated.
[346/495] Building CXX object src/CMakeFiles/cataclysm-bn-tiles-common.dir/vehicle_move.cpp.o
/var/home/scarf/repo/cata/Cataclysm/src/vehicle_move.cpp:662:17: warning: unused variable 'weight_factor' [-Wunused-variable]
  662 |     const float weight_factor = mass >= mass2 ?
      |                 ^~~~~~~~~~~~~
1 warning generated.

Checklist

Mandatory

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax like closes #1234 in Summary of the PR so it can be closed automatically.
• I've committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.