[TASK] Remove additional Fluid links (TYPO3-Documentation#1974)

In the Introduction page, there was an additional section with
links to external sources. This is now mostly redundant, as
more information has been included in the Fluid chapter. For
example the page "Syntax" was included, so it is no longer
necessary to link to external source. Also, some of the links
are duplicates with the links already included on the page
"Using Fluid in TYPO3".

Related: TYPO3-Documentation/TYPO3CMS-Book-ExtbaseFluid#536

Documentation/ApiOverview/Fluid/Introduction.rst

@@ -278,28 +278,3 @@ Set the Fluid paths with TypoScript using :ref:`t3tsref:cobj-fluidtemplate`
          <p> some text </p>
       </div>
    </div>
-
-
-
-Further information
-===================
-
-To get an introduction to the basics of Fluid:
-
-* `The Fluid Syntax <https://github.com/TYPO3/Fluid/blob/main/doc/FLUID_SYNTAX.md>`__
-* `ViewHelpers - what these classes do in the Fluid language <https://github.com/TYPO3/Fluid/blob/main/doc/FLUID_VIEWHELPERS.md>`__
-
-You may want to follow one of these comprehensive
-tutorials:
-
-* :doc:`t3sitepackage:Index` which shows you how to create a theme for your site
-  using Fluid.
-* :ref:`Create custom content elements <adding-your-own-content-elements>`
-* :doc:`t3extbasebook:Index`
-* Use Fluid to create emails using the :ref:`TYPO3 Mail API <mail-fluid-email>`
-
-Once you have successfully completed your fist steps, these references might come
-in handy:
-
-* `24 TIPS & TRICKS FOR FLUID <https://usetypo3.com/24-fluid-tips.html>`__
-* :doc:`Fluid Viewhelper Reference <t3viewhelper:Index>`