fix for shadows global declaration warning

[JacobBarthelmeh]

On my local machine was hitting this warning with ./configure --enable-all && make

ake install  CC       tests/api/unit_test-test_ossl_x509_ext.o
src/internal.c: In function 'DisplaySecTrustError':
src/internal.c:42224:14: warning: declaration of 'buffer' shadows a global declaration [-Wshadow]
42224 |         char buffer[256];
      |              ^~~~~~
In file included from src/internal.c:95:
./wolfssl/internal.h:2129:29: note: shadowed declaration is here
 2129 | typedef WOLFSSL_BUFFER_INFO buffer;
      |                             ^~~~~~

bash-3.2$ gcc -v
Using built-in specs.
Target: x86_64-apple-darwin22.6.0
gcc version 15.2.0 (GCC) 

[devin-ai-integration]

🛟 Devin Lifeguard found 1 likely issues in this PR

• limit-stack-usage snippet: Apply the WOLFSSL_SMALL_STACK pattern by replacing char buf[256]; with a dynamically allocated buffer (e.g., char* buf = (char*)XMALLOC(256, NULL, DYNAMIC_TYPE_TMP_BUFFER);) and freeing it after use.

@JacobBarthelmeh
please take a look at the above issues which Devin flagged. Devin will not fix these issues automatically.

[JacobBarthelmeh]

Retest this please Jenkins