We were going to great effort to include the normal directories in the
GJS search path and the code to to do this broke recently when
jsdir and jsnativedir were moved to gjs-internals-1.0.pc. However, it
was actually unnecessary since the standard directories are appended
to the default path.

(We continue to use a GNOME_SHELL_JS envvar separate from GJS_PATH
for the Shell to enable the somewhat unlikely case where someone wants
to invoke the shell specifying a GJS_PATH.)