Docs: Specify tools version

To have the better generated documentation format, sphinx should be
2.0.1 and docutils should be 0.16.
Package librsvg2-bin is needed by sphinxcontrib-svg2pdfconverter.

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: Id001bf742378d6675ae3f5a73a6035824c8e4b2d
diff --git a/docs/technical_references/instructions/documentation_generation.rst b/docs/technical_references/instructions/documentation_generation.rst
index 29032be..da21dee 100644
--- a/docs/technical_references/instructions/documentation_generation.rst
+++ b/docs/technical_references/instructions/documentation_generation.rst
@@ -116,11 +116,12 @@
 The following tools are needed:
 
     - Python3 and the following modules:
-    - Sphinx v1.7.9
+    - Sphinx v2.0.1
     - m2r v0.2.0
     - sphinxcontrib-plantuml
     - sphinxcontrib-svg2pdfconverter
     - sphinx-rtd-theme
+    - docutils v0.16
     - Graphviz dot v2.38.0 or later
     - PlantUML v1.2018.11 or later
     - Java runtime environment 1.8 or later (for running PlantUML)
@@ -135,7 +136,7 @@
 
         .. code-block:: bash
 
-            sudo apt-get install -y python3 graphviz default-jre
+            sudo apt-get install -y python3 graphviz default-jre librsvg2-bin
             pip install -r tools/requirements.txt
             mkdir ~/plantuml
             curl -L http://sourceforge.net/projects/plantuml/files/plantuml.jar/download --output ~/plantuml/plantuml.jar