Bug 1530837 [wpt PR 15524] - Update README and META.yml to use the Ma…

…thML Core spec., a=testonly

Automatic update from web-platform-tests
Update README and META.yml to use the MathML Core spec. (#15524)

Meta help still needs to be updated.
--

wpt-commits: 1d89f3761c2a5b25dadf6dc4d868b0d6a8ea0bfc
wpt-pr: 15524

testing/web-platform/tests/mathml/META.yml

@@ -1,3 +1,3 @@
-spec: http://www.mathml-association.org/MathMLinHTML5/
+spec: https://mathml-refresh.github.io/mathml-core/
 suggested_reviewers:
   - fred-wang

testing/web-platform/tests/mathml/README.md

@@ -1,13 +1,7 @@
-# MathML: Tests for the MathML in HTML5 implementation note
+# MathML: Tests for the MathML Core specification
 
 This directory contains tests for the
-[MathML in HTML5 implementation note](http://www.mathml-association.org/MathMLinHTML5/)
-which is itself based on the
-[HTML5 W3C recommendation](https://www.w3.org/TR/html5/),
-on the [MathML3 W3C recommendation](https://www.w3.org/TR/MathML3/)
-and on the
-[Open Font Format 3](http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=66391) standard.
-
+[MathML Core specification](https://mathml-refresh.github.io/mathml-core/).
 Many of the tests verify OpenType features and require specific Web fonts for
 that purpose. WOFF fonts are generated by scripts in the `tools/` folder using
 the Python API of