ptx: Extra space is added before truncation marker

[Misakait]

When text is truncated, uutils/ptx incorrectly adds a leading space before the truncation marker in both roff (-G) formats and tex formats, which is inconsistent with GNU ptx.

Steps to Reproduce

Run the following command with GNU ptx:

echo "Hello  World\nRust is funnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn" | ptx -G -w 30

The output for the keyword "is" contains "is/".

but run the same command with uutils/ptx:

echo "Hello  World\nRust is funnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn" |cargo run -- -G -w 30

The output for the keyword "is" contains "is /".

of course,multiple spaces between words also trigger this bug.

[Misakait]

I've investigated this bug and have a fix ready. I would like to submit a pull request for it.