read and discard prober response body (sigstore#1349)

Signed-off-by: Bob Callaway <bcallaway@google.com>

change in-cluster prober to read across all shards (programatically) (s…

…igstore#1333)

Signed-off-by: Bob Callaway <bcallaway@google.com>

go mod tidy (sigstore#1329)

Signed-off-by: Bob Callaway <bcallaway@google.com>