ref-manual, yocto-project-qs, poky.ent: Fixed CentOS package

Fixes [YOCTO #12467]

Changed the CentOS variable to use python34-pip
instead of python3-pip. Removed notes indicating
CentOS 6.x exceptions because this version does
not support CentOS 6.x.

(From yocto-docs rev: 7134eb2ac156b86ef844a9a46c4a8a9444ff6770)

Signed-off-by: Kristi Rifenbark <kristi@buzzcollectivemarketing.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/poky.ent

@@ -71,5 +71,4 @@
      python3-pexpect">
 <!ENTITY CENTOS_HOST_PACKAGES_ESSENTIAL "gawk make wget tar bzip2 gzip python unzip perl patch \
      diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath socat \
-     perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue python3-pip python3-pexpect">
+     perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue python34-pip python3-pexpect">
-

documentation/ref-manual/introduction.xml

@@ -351,18 +351,6 @@
             <para>
                 The following list shows the required packages by function
                 given a supported CentOS Linux distribution:
-                <note>
-                    For CentOS 6.x, some of the versions of the components
-                    provided by the distribution are too old (e.g. Git, Python,
-                    and tar).
-                    It is recommended that you install the buildtools in order
-                    to provide versions that will work with the OpenEmbedded
-                    build system.
-                    For information on how to install the buildtools tarball,
-                    see the
-                    "<link linkend='required-git-tar-and-python-versions'>Required Git, Tar, and Python Versions</link>"
-                    section.
-                </note>
                 <itemizedlist>
                     <listitem><para><emphasis>Essentials:</emphasis>
                         Packages needed to build an image for a headless

documentation/yocto-project-qs/yocto-project-qs.xml

@@ -322,14 +322,6 @@
      $ sudo yum install &CENTOS_HOST_PACKAGES_ESSENTIAL; \
      SDL-devel xterm
                         </literallayout>
-                        <note>
-                            CentOS 6.x users need to ensure that the required
-                            versions of Git, tar and Python are available.
-                            For details, See the
-                            "<ulink url='&YOCTO_DOCS_REF_URL;#required-git-tar-and-python-versions'>Required Git, tar, and Python Versions</ulink>"
-                            section in the Yocto Project Reference Manual for
-                            information.
-                        </note>
                         </para></listitem>
                 </itemizedlist>
             </para>