build: clear 8 warnings - && inside || without parentheses (#15587)

Every edit makes the precedence the compiler already applies explicit. None
of them regroups an expression, so behavior is unchanged at all eight sites.
Strip parentheses and whitespace from the diff and the token stream matches.

GCodeProcessor.cpp:1472 tests == where the symmetric clause below tests !=,
which reads like a typo and is not one. A comment now explains why.

OrcaSlicer.cpp:4760 was the only judgment call. Its leading !is_seq_print is
bare while both operands are parenthesized, so the written form matches what
the compiler does. Kept rather than guessed at.

src/slic3r/GUI/Plater.cpp

@@ -3667,8 +3667,8 @@ void Sidebar::update_presets(Preset::Type preset_type)
                 // so extruders without an explicit sub-nozzle count never offer Hybrid. A nullable-int
                 // nil is INT_MAX (> 1) and would otherwise falsely pass the gate, so exclude it too.
                 if (boost::algorithm::contains(extruder_variants->values[index], type + " " + nozzle_volumes_def->enum_labels[i]) ||
-                    extruder_max_nozzle_count->get_at(index) > 1 && extruder_max_nozzle_count->get_at(index) != ConfigOptionIntsNullable::nil_value() &&
-                    nozzle_volumes_def->enum_keys_map->at(nozzle_volumes_def->enum_values[i]) == nvtHybrid) {
+                    (extruder_max_nozzle_count->get_at(index) > 1 && extruder_max_nozzle_count->get_at(index) != ConfigOptionIntsNullable::nil_value() &&
+                    nozzle_volumes_def->enum_keys_map->at(nozzle_volumes_def->enum_values[i]) == nvtHybrid)) {
                     if (nozzle_volumes_def->enum_keys_map->at(nozzle_volumes_def->enum_values[i]) == NozzleVolumeType::nvtHighFlow &&(diameter == "0.2" ||
                         is_skip_high_flow_printer(printer_model)))
                         continue;