Update readme -- replace Catch2 with doctest [ci skip]

README.md

@@ -199,7 +199,7 @@ a separate license:
 | [json include file](http://jsoncpp.sourceforge.net) | `packages/seacas/libraries/ioss/src/visualization/` | [MIT](https://opensource.org/licenses/MIT) |
 | [terminal_color](https://github.com/matovitch/trmclr) | `packages/seacas/libraries/aprepro_lib` | [zlib](https://opensource.org/licenses/zlib) |
 | [Tessil Hash](https://github.com/Tessil/) | `packages/seacas/libraries/ioss/src/hash` |  [MIT](https://opensource.org/licenses/MIT) |
-| [Catch2](https://github.com/catchorg/Catch2) | `packages/seacas/libraries/ioss/src/catch.hpp` | [Boost](http://www.boost.org/LICENSE_1_0.txt) |
+| [doctest](https://github.com/doctest/doctest) | `packages/seacas/libraries/ioss/src/doctest.h` | [MIT](https://opensource.org/licenses/MIT) |
 | [pdqsort](https://github.com/orlp/pdqsort) | `packages/seacas/libraries/ioss/src` | [Zlib License](https://github.com/orlp/pdqsort/blob/master/license.txt) |
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