gst-inspect: Re-add DEFAULT_LESS_OPTS with initial value
Commit 56b4fbef refactored the pipe code to use GLib utility, but the patch was hading some other changed. LESS env was now hardcoded in the middle instead of from a define and was changed from FXR to -RX. The "-" is not even valid for LESS env, and with the lost of F, we would still use a pager when the content fits the terminal.