libheif: remove ports-gcc workaround

from Brad

multimedia/libheif/patches/patch-libheif_CMakeLists_txt

@@ -1,14 +0,0 @@
-gcc8: undefined reference to `std::filesystem::__cxx11::path::_M_split_cmpts()'
-
-Index: libheif/CMakeLists.txt
---- libheif/CMakeLists.txt.orig
-+++ libheif/CMakeLists.txt
-@@ -243,6 +243,8 @@ target_compile_definitions(heif
-         LIBHEIF_EXPORTS
-         HAVE_VISIBILITY)
- 
-+target_link_libraries(heif PUBLIC $<$<AND:$<CXX_COMPILER_ID:GNU>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,9.0>>:stdc++fs>)
-+
- if (PLUGIN_LOADING_SUPPORTED_AND_ENABLED)
-     target_compile_definitions(heif PRIVATE ENABLE_PLUGIN_LOADING=1)
-     target_link_libraries(heif PRIVATE ${CMAKE_DL_LIBS})