LibGfx/PortableFormat: Use `static_cast` instead of C-style casts

Userland/Libraries/LibGfx/ImageFormats/PGMLoader.cpp

@@ -39,7 +39,7 @@ ErrorOr<void> read_image_data(PGMLoadingContext& context)
 
             TRY(read_whitespace(context));
 
-            color_data[i] = { (u8)value, (u8)value, (u8)value };
+            color_data[i] = { static_cast<u8>(value), static_cast<u8>(value), static_cast<u8>(value) };
         }
     } else if (context.type == PGMLoadingContext::Type::RAWBITS) {
         for (u64 i = 0; i < context_size; ++i) {

Userland/Libraries/LibGfx/ImageFormats/PPMLoader.cpp

@@ -29,7 +29,7 @@ ErrorOr<void> read_image_data(PPMLoadingContext& context)
             auto const blue = TRY(read_number(stream));
             TRY(read_whitespace(context));
 
-            Color color { (u8)red, (u8)green, (u8)blue };
+            Color color { static_cast<u8>(red), static_cast<u8>(green), static_cast<u8>(blue) };
             if (context.format_details.max_val < 255)
                 color = adjust_color(context.format_details.max_val, color);
             color_data[i] = color;