[Bug] compiler warning for demo

[mgerhardy]

Bug description

[127/156] Building CXX object src/tests/testimgui/CMakeFiles/testimgui.dir/implot_demo.cpp.o
src/tests/testimgui/implot_demo.cpp: In function ‘void ImPlot::Demo_LegendOptions()’:
src/tests/testimgui/implot_demo.cpp:1899:54: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
 1899 |             snprintf(label, sizeof(label), "Item %03d", i+4);
      |                                                      ^
src/tests/testimgui/implot_demo.cpp:1899:21: note: ‘snprintf’ output between 9 and 17 bytes into a destination of size 16
 1899 |             snprintf(label, sizeof(label), "Item %03d", i+4);

compiler: g++ (Debian 14.2.0-19) 14.2.0