[tests] Remove unused function InsecureRandBytes(size_t len)

src/test/test_bitcoin.h

@@ -33,7 +33,6 @@ static inline uint256 InsecureRand256() { return insecure_rand_ctx.rand256(); }
 static inline uint64_t InsecureRandBits(int bits) { return insecure_rand_ctx.randbits(bits); }
 static inline uint64_t InsecureRandRange(uint64_t range) { return insecure_rand_ctx.randrange(range); }
 static inline bool InsecureRandBool() { return insecure_rand_ctx.randbool(); }
-static inline std::vector<unsigned char> InsecureRandBytes(size_t len) { return insecure_rand_ctx.randbytes(len); }
 
 /** Basic testing setup.
  * This just configures logging and chain parameters.