ci: temporarily set -Wno-deprecated-declarations in Packit

to suppress OpenSSL 3.0 deprecation warnings (until a proper solution
is deployed):

```
../src/shared/creds-util.c: In function ‘sha256_hash_host_and_tpm2_key’:
../src/shared/creds-util.c:412:9: error: ‘SHA256_Init’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  412 |         if (SHA256_Init(&sha256_context) != 1)
      |         ^~
In file included from /usr/include/openssl/x509.h:41,
                 from ../src/shared/openssl-util.h:8,
                 from ../src/shared/creds-util.c:21:
/usr/include/openssl/sha.h:73:27: note: declared here
   73 | OSSL_DEPRECATEDIN_3_0 int SHA256_Init(SHA256_CTX *c);
      |                           ^~~~~~~~~~~
../src/shared/creds-util.c:415:9: error: ‘SHA256_Update’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  415 |         if (host_key && SHA256_Update(&sha256_context, host_key, host_key_size) != 1)
      |         ^~
In file included from /usr/include/openssl/x509.h:41,
                 from ../src/shared/openssl-util.h:8,
                 from ../src/shared/creds-util.c:21:
/usr/include/openssl/sha.h:74:27: note: declared here
   74 | OSSL_DEPRECATEDIN_3_0 int SHA256_Update(SHA256_CTX *c,
      |                           ^~~~~~~~~~~~~
../src/shared/creds-util.c:418:9: error: ‘SHA256_Update’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  418 |         if (tpm2_key && SHA256_Update(&sha256_context, tpm2_key, tpm2_key_size) != 1)
      |         ^~
In file included from /usr/include/openssl/x509.h:41,
                 from ../src/shared/openssl-util.h:8,
                 from ../src/shared/creds-util.c:21:
/usr/include/openssl/sha.h:74:27: note: declared here
   74 | OSSL_DEPRECATEDIN_3_0 int SHA256_Update(SHA256_CTX *c,
      |                           ^~~~~~~~~~~~~
../src/shared/creds-util.c:421:9: error: ‘SHA256_Final’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  421 |         if (SHA256_Final(ret, &sha256_context) != 1)
      |         ^~
In file included from /usr/include/openssl/x509.h:41,
                 from ../src/shared/openssl-util.h:8,
                 from ../src/shared/creds-util.c:21:
/usr/include/openssl/sha.h:76:27: note: declared here
   76 | OSSL_DEPRECATEDIN_3_0 int SHA256_Final(unsigned char *md, SHA256_CTX *c);
      |                           ^~~~~~~~~~~~
cc1: all warnings being treated as errors

```