impl : use 6 digits for tensor dims (ggml-org#20094)

Many models have vocabulary sizes, and thus tensor shapes, with more
than 5 digits (ex: Gemma 3's vocab size is 262,208).

I already fixed this for `llama_format_tensor_shape` but missed it for
`llama_format_tensor_shape` until now. Oops.

Author: ddh0

src/llama-impl.cpp

@@ -100,9 +100,9 @@ std::string format(const char * fmt, ...) {
 
 std::string llama_format_tensor_shape(const std::vector<int64_t> & ne) {
     char buf[256];
-    snprintf(buf, sizeof(buf), "%5" PRId64, ne.at(0));
+    snprintf(buf, sizeof(buf), "%6" PRId64, ne.at(0));
     for (size_t i = 1; i < ne.size(); i++) {
-        snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), ", %5" PRId64, ne.at(i));
+        snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), ", %6" PRId64, ne.at(i));
     }
     return buf;
 }