Fix: ./install.sh: option requires an argument -- h

[fidergo-stephane-gourichon]

Calling install.sh -h failed to show the script usage. The -h option of install.sh did not work and script just went on with default settings.

From getopt man page:

Each short option character in shortopts may be followed by one colon to indicate it has a required argument, and by two colons to indicate it has an optional argument.

-h option did not actually require argument but was followed by a colon, causing the error. Thus, removed extraneous colon.

Result: calling install.sh -h now works, shows the script usage and stops the script as intended.

[soumith]

thanks!