libgit2: fix build (#7721)

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=46031

projects/libgit2/build.sh

@@ -32,7 +32,6 @@ do
     fuzzer_name=$(basename "${fuzzer%.c}")
 
     $CC $CFLAGS -c -I./src -I../src/libgit2 -I../src/util -I../include \
-        -DLIBGIT2_NO_FEATURES_H \
         "$fuzzer" -o "$WORK/$fuzzer_name.o"
     $CXX $CXXFLAGS -std=c++11 -o "$OUT/$fuzzer_name" \
         $LIB_FUZZING_ENGINE "$WORK/$fuzzer_name.o" "$WORK/lib/libgit2.a"