cmake: bump minimum GnuTLS version to 3.7.4

We need gnutls_ciphersuite_get which was introduced in 3.7.4.

Author: travisdowns

cmake/SeastarDependencies.cmake

@@ -88,7 +88,7 @@ macro (seastar_find_dependencies)
   endif()
   seastar_find_dep (fmt 8.1.1 REQUIRED)
   seastar_find_dep (lz4 1.7.3 REQUIRED)
-  seastar_find_dep (GnuTLS 3.3.26 REQUIRED)
+  seastar_find_dep (GnuTLS 3.7.4 REQUIRED)
   if (Seastar_IO_URING)
     seastar_find_dep (LibUring 2.0 REQUIRED)
   endif()