Fix parse error for show-pins.pl

[robamu]

This fix worked for me, but I am not a perl expert, I simply tried to apply a script fix from another repository on this version of the script.

See https://github.com/mvduin/bbb-pin-utils/commit/d51ed53ef61935a5e1289d141e9fdd974e2a4f99 for additional information.

[RobertCNelson]

Thanks @robamu