installer: don't install node_internals.h

As the name suggests, it's for internal use only, so don't install it.

Including it in an add-on doesn't work because the file depends on other
header files that are not installed.

Adding it to the install list appears to have been an oversight in
commit 32478ac ("build: unix install node and dep library headers").

PR-URL: #6913
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Robert Jefe Lindstaedt <robert.lindstaedt@gmail.com>

tools/install.py

@@ -150,7 +150,6 @@ def headers(action):
     'config.gypi',
     'src/node.h',
     'src/node_buffer.h',
-    'src/node_internals.h',
     'src/node_object_wrap.h',
     'src/node_version.h',
   ], 'include/node/')