docs: fixed bitcoin-cli -help output for help2man
docs: fixed bitcoin-cli -help output for help2man

The `help2man` parses a string containing two spaces between words with an issue:
it gives out `.TP` and `.IP` commands instead of a single `.IP` command.
Removing an extra space fixes this issue.
Currently the `-help` output for the `-stdin` option looks without any issue due to eliminating
of two spaces between words by a `FormatParagraph` call for this particular case.
For consistency and preventing from future regressions extra spaces have been removed from the both lines.
The redundant `strprintf` call has been removed aswell.

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