Merge #16752: doc: Delete stale URL in test README

41d484d doc: Delete stale URL in test README (Michael Folkson)

Pull request description:

  The resource on the Boost unit test framework previously linked to in src/test/README.md was a stale URL.

  Instead of deleting it, I've replaced it with an alternative resource on the framework on [boost.org](https://www.boost.org/doc/libs/1_45_0/libs/test/doc/html/utf/tutorials.html).

ACKs for top commit:
  promag:
    ACK 41d484d.
  hebasto:
    ACK 41d484d, the removed link is really obsolete.
  fanquake:
    ACK 41d484d - Thanks.

Tree-SHA512: 764f12548441bde615f77b7a2ca7c5188b4ab936972d16b84960fbd8604d4cbd224415bc59ce839e7e63293aa84fd97f31a69e38734e531231cdb0e148d2e1bd

Author: fanquake

src/test/README.md

@@ -49,7 +49,3 @@ unit tests.  The file naming convention is `<source_filename>_tests.cpp`
 and such files should wrap their tests in a test suite
 called `<source_filename>_tests`. For an example of this pattern,
 examine `uint256_tests.cpp`.
-
-For further reading, I found the following website to be helpful in
-explaining how the boost unit test framework works:
-[http://www.alittlemadness.com/2009/03/31/c-unit-testing-with-boosttest/](http://archive.is/dRBGf).