Stop including %doc in -devel packages

The documentation files are already included once in installation paths
underneath the crate directory. We need them there because the package might
use them in some way, and anyway we don't want to mess with the crate contents.
Adding them a second time under /usr/share/doc creates duplication. People
generally don't install rust-*-devel packages, and it doesn't make much sense
to provide documentation.

Fixes https://pagure.io/fedora-rust/rust2rpm/issue/164.

rust2rpm/templates/main.spec

@@ -160,9 +160,6 @@ use {% if feature is not none %}the "{{ feature }}" feature of {% endif %}the "%
       {% if license_files|length > 0 %}
 %license {{ license_files|join(' ') }}
       {% endif %}
-      {% if doc_files|length > 0 %}
-%doc {{ doc_files|join(' ') }}
-      {% endif %}
 %{cargo_registry}/%{crate}-%{version_no_tilde}/
     {% else %}
 %ghost %{cargo_registry}/%{crate}-%{version_no_tilde}/Cargo.toml