We dont actually need vzeroupper at start of function

GCC emits vzeroupper automatically when compiling with native
optimizations but we still need it otherwise

kitty/simd-string-impl.h

@@ -297,7 +297,6 @@ FUNC(zero_last_n_bytes)(integer_t vec, const integer_t index, char n) {
 }
 
 #define find_match(haystack, sz, get_test_vec) { \
-    /* zero_upper(); this is disabled as some buggy compilers re-order instructions causing the test result vec to be zero after the test */\
     const uint8_t* limit = haystack + sz; \
     integer_t chunk; int n; \
 \