tools: install doc tools only when necessary
Marking tools/doc/node_modules as PHONY result in constant
installation of the doctools whether it's changed or not
(which means make lint-addon-docs
always install the tools).
Unmark it and fix the dependency to avoid unnecessary
installations if the package.json is not changed.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
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