chore: resolve constVariable linter error

Author: kwvg

src/hash_x11.h

@@ -37,7 +37,7 @@ inline uint256 HashX11(const T1 pbegin, const T1 pend)
     sph_shavite512_context ctx_shavite;
     sph_simd512_context ctx_simd;
     sph_echo512_context ctx_echo;
-    static unsigned char pblank[1];
+    static const unsigned char pblank[1]{};
 
     uint512 hash[11];