Bug 1564732 [wpt PR 17631] - [docs] Fix internal links, a=testonly

Automatic update from web-platform-tests
[docs] Fix internal links (#17631)

--

wpt-commits: b0e5cf1b0940b31dc8123cee45968e56525edb29
wpt-pr: 17631

testing/web-platform/tests/docs/writing-tests/css-metadata.md

@@ -92,7 +92,7 @@ href="https://www.w3.org/TR/CSS21/colors.html#background-properties" />
 
 The following flags are **deprecated** and should not be declared by new tests.
 Tests which satisfy the described criteria should simply be designated as
-"manual" using [the `-manual` file name flag][file-name-flags].
+"manual" using [the `-manual` file name flag](file-names).
 
 <table>
 <tr>
@@ -189,5 +189,3 @@ Examples of good test assertions:
 * "This test checks that 'text-indent' affects only the first line
   of a block container if that line is also the first formatted line
   of an element."
-
-[file-name-flags]: {{ site.baseurl }}{% link _writing-tests/file-names.md %}

testing/web-platform/tests/docs/writing-tests/general-guidelines.md

@@ -126,8 +126,7 @@ w3c-test.org. When these tests are run on CI systems they are
 typically configured with access to external resources disabled, so
 tests that try to access them will fail. Where tests want to use
 multiple hosts this is possible through a known set of subdomains and
-the
-[text substitution features of wptserve]({{ site.baseurl }}{% link writing-tests/server-features.md %}#tests-involving-multiple-origins).
+the [text substitution features of wptserve](server-features).
 
 
 ### Be Self-Describing

testing/web-platform/tests/docs/writing-tests/reftests.md

@@ -83,7 +83,7 @@ href=c.html>`,
 
 Or, graphically:
 
-<img src="{{ site.baseurl }}{% link assets/reftest_graph_example.svg %}"
+<img src="../_static/reftest_graph_example.svg"
      alt="diagram of the above reftest graph as a directed graph">
 
 In this case, to pass we must either have `a.html`, `b.html` and