[clang-tidy] fix building clang-tidy documentation.

[etienneb]

Summary

The clang-tidy documentation can't be generated because of broken links.

Warning, treated as error:
/home/etienneb/llvm/llvm/tools/clang/tools/extra/docs/clang-tidy/checks/google-readability-function-size.rst:: WARNING: document isn't included in any toctree

[alexfh]

LG. Thank you!

docs/clang-tidy/checks/list.rst

.. toctree::
    cppcoreguidelines-pro-type-static-cast-downcast
    cppcoreguidelines-pro-type-union-access
    cppcoreguidelines-pro-type-vararg
    google-build-explicit-make-pair
    google-build-namespaces
    google-build-using-namespace
    google-explicit-constructor
    google-global-names-in-headers
-   google-readability-braces-around-statements (redirects to readability-braces-around-statements) <readability-braces-around-statements>
+   google-readability-braces-around-statements (redirects to readability-braces-around-statements) <google-readability-braces-around-statements>
    google-readability-casting
-   google-readability-function-size (redirects to readability-function-size) <readability-function-size>
+   google-readability-function-size (redirects to readability-function-size) <google-readability-function-size>
    google-readability-namespace-comments
    google-readability-redundant-smartptr-get
    google-readability-todo
    google-runtime-int
    google-runtime-member-string-references
    google-runtime-memset
    google-runtime-operator
    google-runtime-references

docs/clang-tidy/checks/readability-static-definition-in-anonymous-namespace.rst

 .. title:: clang-tidy - readability-static-definition-in-anonymous-namespace
 
 readability-static-definition-in-anonymous-namespace
 ====================================================
 
 Finds static function and variable definitions in anonymous namespace.
 
 In this case, ``static`` is redundant, because anonymous namespace limits the
 visibility of definitions to a single translation unit.
 
 .. code:: c++
+
   namespace {
     static int a = 1; // Warning.
     static const b = 1; // Warning.
   }
 
 The check will apply a fix by removing the redundant ``static`` qualifier.