Make mixed sequence type notification less wordy
Make mixed sequence type notification less wordy

The reason to do so comes from the discussion in #401.

In hindsight, it is probably not relevant to tell users to try one
sequence at a time. We only need to make them aware that they have
mixed nucleotide and amino-acid sequences and that it is not allowed.

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

yeban/sequenceserver,yeban/sequenceserver,yeban/sequenceserver,yeban/sequenceserver