common, server : use the same User-Agent by default (#18957)

This commit also ensures that if a custom User-Agent is used, it will be
the only one sent.

Signed-off-by: Adrien Gallouët <angt@huggingface.co>

tools/server/server-common.cpp

@@ -779,7 +779,6 @@ static void handle_media(
         // download remote image
         // TODO @ngxson : maybe make these params configurable
         common_remote_params params;
-        params.headers.push_back({"User-Agent", "llama.cpp/" + build_info});
         params.max_size = 1024 * 1024 * 10; // 10MB
         params.timeout  = 10; // seconds
         SRV_INF("downloading image from '%s'\n", url.c_str());