[clang-doc] remove indentation for preformatted text (llvm#166672)

Text that is in between `<pre>` tags is formatted verbatim. Thus, the
text that was correctly indented in relation to its depth in HTML was
being indented incorrectly when rendered. That resulted in bad looking pages.

Author: evelez7

clang-tools-extra/clang-doc/assets/class-template.mustache

@@ -141,9 +141,7 @@
                 <div>
                     {{#PublicMembers}}
                     <div id="{{Name}}" class="delimiter-container">
-                        <pre>
-                            <code class="language-cpp code-clang-doc" >{{Type}} {{Name}}</code>
-                        </pre>
+                        <pre><code class="language-cpp code-clang-doc" >{{Type}} {{Name}}</code></pre>
                         {{#MemberComments}}
                         <div>
                             {{>Comments}}
@@ -160,9 +158,7 @@
                 <div>
                     {{#Obj}}
                     <div id="{{Name}}" class="delimiter-container">
-                        <pre>
-<code class="language-cpp code-clang-doc" >{{Type}} {{Name}}</code>
-                        </pre>
+                        <pre><code class="language-cpp code-clang-doc" >{{Type}} {{Name}}</code></pre>
                         {{#MemberComments}}
                         <div>
                             {{>Comments}}

clang-tools-extra/clang-doc/assets/namespace-template.mustache

@@ -92,9 +92,7 @@
                         {{#Records}}
                             <li id="{{USR}}" style="max-height: 40px;">
                                 <a href="{{DocumentationFileName}}.html">
-                                    <pre>
-                                        <code class="language-cpp code-clang-doc">class {{Name}}</code>
-                                    </pre>
+                                    <pre><code class="language-cpp code-clang-doc">class {{Name}}</code></pre>
                                 </a>
                             </li>
                         {{/Records}}

clang-tools-extra/test/clang-doc/mustache-index.cpp

@@ -70,9 +70,7 @@ class Foo;
 // CHECK-NEXT:      <ul class="class-container">
 // CHECK-NEXT:          <li id="{{[0-9A-F]*}}" style="max-height: 40px;">
 // CHECK-NEXT:              <a href="_ZTV3Foo.html">
-// CHECK-NEXT:                  <pre>
-// CHECK-NEXT:                      <code class="language-cpp code-clang-doc">class Foo</code>
-// CHECK-NEXT:                  </pre>
+// CHECK-NEXT:                  <pre><code class="language-cpp code-clang-doc">class Foo</code></pre>
 // CHECK-NEXT:              </a>
 // CHECK-NEXT:          </li>
 // CHECK-NEXT:      </ul>

clang-tools-extra/test/clang-doc/mustache-separate-namespace.cpp

@@ -9,9 +9,7 @@ namespace MyNamespace {
 // CHECK:       <ul class="class-container">
 // CHECK-NEXT:    <li id="{{[0-9A-F]*}}" style="max-height: 40px;">
 // CHECK-NEXT:        <a href="_ZTVN11MyNamespace3FooE.html">
-// CHECK-NEXT:            <pre>
-// CHECK-NEXT:                <code class="language-cpp code-clang-doc">class Foo</code>
-// CHECK-NEXT:            </pre>
+// CHECK-NEXT:            <pre><code class="language-cpp code-clang-doc">class Foo</code></pre>
 // CHECK-NEXT:        </a>
 // CHECK-NEXT:    </li>
 // CHECK-NEXT: </ul>