fix compressed count regression

[pancelor]

repro: echo 'abc=3' | shrinko8 --count --minify - -

before this commit, this command showed stats for
tokens and chars, but not compressed

now, it also shows compressed

---

sometime between 15304da and now, the code changed:

# 15304da
if not (args.output and str(args.format) not in CartFormat.src_names) and not args.no_count_compress: # else, will be done in write_cart

# before this commit
if not (args.output and args.format.is_src()) and not args.no_count_compress: # else, will be done in write_cart

The difference is str(args.format) not in CartFormat.src_names -> args.format.is_src(), which is missing a not. fixed!

[pancelor]

On second though, the # else, will be done in write_cart comment confuses me; it seems out-of-date, possibly? this is the only place in the whole project where write_compressed_size is used

[thisismypassport]

Oops! - thanks, taken

(write_compressed_size is done to compute & print the compressed size when we won't do this anyway as part of write_cart)