memory: remove unreachable res operand in wolfSSL_Realloc

Premise:  memory.c:1337 `void* res = 0;` -- and every subsequent write to res
          lies on a path that cannot reach the claimed condition.
Claim:    memory.c:1414 `if (pt != NULL && res == NULL)` -- the `res == NULL`
          operand.
Proof:    res is assigned in exactly two places before :1414.
          (a) :1353 `res = realloc(ptr, size)` sits inside the
              `if (heap == NULL && globalHeapHint == NULL)` arm at :1348, while
              :1414 sits inside that if's else arm -- mutually exclusive.
          (b) :1394/:1397 sit in the fixed-IO-pool arm at :1387, while :1414
              sits in the `/* general memory */` else arm at :1402 -- again
              mutually exclusive.
          Everything else on the path either returns (the WOLFSSL_HEAP_TEST
          shortcut at :1342, the ptr == NULL case at :1371, the mutex-lock
          failure at :1379) or writes only pt / i / mem->ava[]. So res still
          holds its 0 initialiser at every evaluation of :1414: the operand is
          invariantly true and its independence pair is unreachable.
Scope:    checked against every combination of WOLFSSL_STATIC_MEMORY,
          WOLFSSL_STATIC_MEMORY_LEAN, WOLFSSL_DEBUG_MEMORY, WOLFSSL_HEAP_TEST,
          WOLFSSL_NO_MALLOC, SINGLE_THREADED and WOLFSSL_MALLOC_CHECK. Under
          WOLFSSL_STATIC_MEMORY_LEAN the #ifndef at :1385 deletes both the
          IO-pool arm and its else, making the :1402 block unconditional --
          and deleting writes (b) along with it, so the argument only gets
          stronger. XREALLOC overrides in types.h either route to this function
          or replace it wholesale; neither can enter it mid-body.
Evidence: llvm-cov MC/DC records this condition's pair as uncovered
          (reports/infra/GAPS.md row 1414:17:1414:42:1).

Compiler cross-check: gcc -O2 emits byte-identical code for this file before
and after this commit -- the optimiser had already folded the removed
condition, independently confirming it was dead.

wolfcrypt/src/memory.c

@@ -1411,7 +1411,7 @@ void* wolfSSL_Realloc(void *ptr, size_t size, void* heap, int type)
                 }
             }
 
-            if (pt != NULL && res == NULL) {
+            if (pt != NULL) {
                 word32 prvSz;
 
                 res = pt->buffer;