Remove obsolete string C header input file

string.h doesn't contain any syscall declarations that need to be
processed by the gen-headers C header file generating utility.

sdk/bpf/c/inc/sol/inc/string.inc

@@ -1,81 +0,0 @@
-#pragma once
-/**
- * @brief Solana string and memory system calls and utilities
- */
-
-#include <sol/types.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/**
- * Copies memory
- */
-static void sol_memcpy(void *dst, const void *src, int len) {
-  for (int i = 0; i < len; i++) {
-    *((uint8_t *)dst + i) = *((const uint8_t *)src + i);
-  }
-}
-
-/**
- * Compares memory
- */
-static int sol_memcmp(const void *s1, const void *s2, int n) {
-  for (int i = 0; i < n; i++) {
-    uint8_t diff = *((uint8_t *)s1 + i) - *((const uint8_t *)s2 + i);
-    if (diff) {
-      return diff;
-    }
-  }
-  return 0;
-}
-
-/**
- * Fill a byte string with a byte value
- */
-static void *sol_memset(void *b, int c, size_t len) {
-  uint8_t *a = (uint8_t *) b;
-  while (len > 0) {
-    *a = c;
-    a++;
-    len--;
-  }
-}
-
-/**
- * Find length of string
- */
-static size_t sol_strlen(const char *s) {
-  size_t len = 0;
-  while (*s) {
-    len++;
-    s++;
-  }
-  return len;
-}
-
-/**
- * Internal memory alloc/free function
- */
-@SYSCALL void* sol_alloc_free_(uint64_t, void *);
-
-/**
- * Alloc zero-initialized memory
- */
-static void *sol_calloc(size_t nitems, size_t size) {
-  return sol_alloc_free_(nitems * size, 0);
-}
-
-/**
- * Deallocates the memory previously allocated by sol_calloc
- */
-static void sol_free(void *ptr) {
-  (void) sol_alloc_free_(0, ptr);
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-/**@}*/