builtin/clone: suppress unexpected default branch advice

In 199f44cb2ead (builtin/clone: allow remote helpers to detect repo, 2024-02-27), clones started partially initializing the refdb before executing the remote helpers by creating a HEAD file and "refs/" directory. This has resulted in some scenarios where git-clone(1) now prints the default branch name advice message where it previously did not. A side-effect of the HEAD file already existing, is that computation of the default branch name is handled later in execution. This matters because prior to 97abaab5f6 (refs: drop `git_default_branch_name()`, 2024-05-17), the default branch value would be computed during its first execution and cached. Subsequent invocations would simply return the cached value. Since the next `git_default_branch_name()` call site, which is invoked through `guess_remote_head()`, is not configured to suppress the advice message, computing the default branch name results in the advice message being printed. Configure `guess_remote_head()` to suppress the advice message, restoring the previous behavior. Signed-off-by: Justin Tobler <jltobler@gmail.com> Acked-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>