Revert #111: allow redirects to data URLs

The rationale for forbidding redirects to data URLs was not sound enough. Therefore this commit
reverts f986c43 which
introduced the restriction.

Overview.html

@@ -2273,11 +2273,8 @@ <h3 id="http-fetch"><span class="secno">5.3 </span>HTTP fetch</h3>
      <var>location</var> with <var>request</var>'s
      <a href="#concept-request-current-url" title="concept-request-current-url">current url</a>.
 
-     <li><p>If <var>locationURL</var> is failure or its
-     <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-scheme" title="concept-url-scheme">scheme</a> is "<code title="">data</code>",
-     return a <a href="#concept-network-error" title="concept-network-error">network error</a>.
-     <!-- If we ever allow redirects to data URLs again make sure to unset the
-          same-origin data-URL flag. -->
+     <li><p>If <var>locationURL</var> is failure, return a
+     <a href="#concept-network-error" title="concept-network-error">network error</a>.
 
      <li><p>If <var>request</var>'s
      <a href="#concept-request-redirect-count" title="concept-request-redirect-count">redirect count</a> is twenty, return a
@@ -2286,6 +2283,8 @@ <h3 id="http-fetch"><span class="secno">5.3 </span>HTTP fetch</h3>
      <li><p>Increase <var>request</var>'s
      <a href="#concept-request-redirect-count" title="concept-request-redirect-count">redirect count</a> by one.
 
+     <li><p>Unset <var title="">request</var>'s <a href="#same-origin-data-url-flag">same-origin data-URL flag</a>.
+
      <li><p>If <var>request</var>'s
      <a href="#concept-request-redirect-mode" title="concept-request-redirect-mode">redirect mode</a> is
      "<code title="">manual</code>", set <var>response</var> to an

Overview.src.html

@@ -2212,11 +2212,8 @@ <h3>HTTP fetch</h3>
      <var>location</var> with <var>request</var>'s
      <span title=concept-request-current-url>current url</span>.
 
-     <li><p>If <var>locationURL</var> is failure or its
-     <span data-anolis-spec=url title=concept-url-scheme>scheme</span> is "<code title>data</code>",
-     return a <span title=concept-network-error>network error</span>.
-     <!-- If we ever allow redirects to data URLs again make sure to unset the
-          same-origin data-URL flag. -->
+     <li><p>If <var>locationURL</var> is failure, return a
+     <span title=concept-network-error>network error</span>.
 
      <li><p>If <var>request</var>'s
      <span title=concept-request-redirect-count>redirect count</span> is twenty, return a
@@ -2225,6 +2222,8 @@ <h3>HTTP fetch</h3>
      <li><p>Increase <var>request</var>'s
      <span title=concept-request-redirect-count>redirect count</span> by one.
 
+     <li><p>Unset <var title>request</var>'s <span>same-origin data-URL flag</span>.
+
      <li><p>If <var>request</var>'s
      <span title=concept-request-redirect-mode>redirect mode</span> is
      "<code title>manual</code>", set <var>response</var> to an