fix tr with delete flag if more than 1 operand given

[BaherSalama]

fixes the issue #5944 where tr -d flag should not take more than one operand
so its like this now

❯ echo "acsd5c"| ./target/debug/tr -d "c"
asd5

~/sad/coreutils main
❯ echo "acsd5c"| ./target/debug/tr -d "c" "p"
./target/debug/tr: extra operand 'p'
Only one string may be given when deleting without squeezing repeats.
Try './target/debug/tr --help' for more information.

problem tho is that adding more arguments errors out tr when it should just display the same massage

where gnu tr

❯ echo "acsd5c"| tr -d "c" "p" "m"
tr: extra operand ‘p’
Try 'tr --help' for more information.

coreutils one

❯ echo "acsd5c"| ./target/debug/tr -d "c" "p" "m"
error: unexpected value 'm' for '[sets]...' found; no more were expected

Usage: ./target/debug/tr [OPTION]... SET1 [SET2]

For more information, try '--help'.

not sure this is related to #5944 since i could not grep for the error expect in whom test so don't know where to look for that

[sylvestre]

looks good but could you please add a test to make sure we don't regress in the future ?
thanks

[BaherSalama]

added a test for 2 operands with -d flag

[cakebaker]

Thanks for your PR :)