dnssec: remove obsolete doc

src/dnssec/doc/api.md

-# API
-
-At this phase of the library development, the API is very unstable and is
-likely to be changing often.
-
-## Conventions for API definitions
-
-- All identifiers are prefixed with `dnssec_` (functions, types) or `DNSSEC_` (constants).
-- All public headers are placed in `lib/dnssec`.
-- Use `#pragma once` in the headers files as a include guard.
-- Includes of other library modules have the following form: `#include <dnssec/module.h>`.
-- Public symbols in the `.c` files are decorated using `_public_` macro from `shared.h`.
-
-## Linking
-
-- Building of static libraries is enabled by default, as shared libraries expose
-  only a public interface. The unit tests perform testing of some internal
-  interfaces, therefore disabling the static build breaks the tests.
-- Installing of static libraries into the system is not recommended.
-
-## TODO
-
-- Decide how to work with `extern "C"`.
-- Autogenerating of public library headers.

src/dnssec/doc/coding.md

-# Coding
-
-## Components Location
-
-- library: `lib` (public headers in `lib/dnssec`)
-- shared: `shared` (shared code for library and utilities, inaccessible from the library)
-- tests: `tests`
-- utilities: `utils`
-
-## Coding Style
-
-Basically, [Linux kernel coding style](https://www.kernel.org/doc/Documentation/CodingStyle) with a few changes is used.
-
-Rules worth to highlight:
-
-- Line limit is 80 chars (if it increases readability, can be exceeded a little).
-- Use tabs for indentation, align with tabs and spaces.
-- Tabs are 8 characters.
-- No white space charactes at the end of the line are allowed.
-- No empty lines at the end of the file, the last line ends with a '\n' char
-- Use braces even for single line statements after if, else, while, for, ...
-- Use typedefs for structs, do not use them for pointers.
-- Use comma after the last element of a list, unless there is a terminating sentinel.