Remove -Wno-shift-op-parentheses for fusl build

fusl/src/multibyte/c16rtomb.c

 #include <uchar.h>
 #include <errno.h>
 #include <wchar.h>
 
 size_t c16rtomb(char *restrict s, char16_t c16, mbstate_t *restrict ps)
 {
         static unsigned internal_state;
         if (!ps) ps = (void *)&internal_state;
         unsigned *x = (unsigned *)ps;
         wchar_t wc;
 
         if (!s) {
                 if (*x) goto ilseq;
                 return 1;
         }
 
         if (!*x && c16 - 0xd800u < 0x400) {
-                *x = c16 - 0xd7c0 << 10;
+                *x = (c16 - 0xd7c0) << 10;
                 return 0;
         }
 
         if (*x) {
                 if (c16 - 0xdc00u >= 0x400) goto ilseq;
                 else wc = *x + c16 - 0xdc00;
                 *x = 0;
         } else {
                 wc = c16;
         }
         return wcrtomb(s, wc, 0);
 
 ilseq:
         *x = 0;
         errno = EILSEQ;
         return -1;
 }