Fix #76: -Wsign-conversion is redundant (#149)

* Fix #76: Remove redundant -Wsign-conversion from CLANG_WARNINGS

-Wconversion already implies -Wsign-conversion for both GCC and Clang,
making the explicit -Wsign-conversion flag redundant in the CLANG_WARNINGS
list. Since GCC_WARNINGS inherits from CLANG_WARNINGS, this removal
applies to both compilers.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: leftibot

cmake/CompilerWarnings.cmake

@@ -51,7 +51,6 @@ function(
         -Woverloaded-virtual # warn if you overload (not override) a virtual function
         -Wpedantic # warn if non-standard C++ is used
         -Wconversion # warn on type conversions that may lose data
-        -Wsign-conversion # warn on sign conversions
         -Wnull-dereference # warn if a null dereference is detected
         -Wdouble-promotion # warn if float is implicit promoted to double
         -Wformat=2 # warn on security issues around functions that format output (ie printf)