docs: Fix typos

Reviewed-by: NMel Kiyama <mkiyama@pivotal.io>
Reviewed-by: NHeikki Linnakangas <hlinnakangas@pivotal.io>

gpdb-doc/dita/install_guide/ansible-example.xml

@@ -21,7 +21,7 @@
     <p>Following are steps to use this Ansible playbook.</p>
     <ol id="ol_umm_h25_yhb">
       <li>Install Ansible on the control node using your package manager. See the <xref
-          href="https://docs.ansible.com" format="html" scope="external">Ansible documention</xref>
+          href="https://docs.ansible.com" format="html" scope="external">Ansible documentation</xref>
         for help with installation.</li>
       <li>Set up passwordless SSH from the control node to all hosts that will be a part of the
         Greenplum Database cluster. You can use the <codeph>ssh-copy-id</codeph> command to install

gpdb-doc/markdown/pxf/gphdfs-pxf-migrate.html.md.erb

@@ -218,7 +218,7 @@ Ensure that you can read from, or write to, each `pxf` external table that you h
 
 ## <a id="remove_gphdfs_ext_table"></a>Removing the gphdfs External Tables
 
-You must remove all `gphdfs` external tables before you can successfuly migrate a Greenplum Database 4 or 5 database to Greenplum 6.
+You must remove all `gphdfs` external tables before you can successfully migrate a Greenplum Database 4 or 5 database to Greenplum 6.
 
 Drop an external table as follows:
 

gpdb-doc/markdown/pxf/jdbc_cfg.html.md.erb

@@ -218,7 +218,7 @@ By default, PXF JDBC user impersonation is disabled.  Perform the following proc
     <property>
         <name>pxf.service.user.impersonation</name>
         <value>true</value>
-    </propery>
+    </property>
     ```
 
 7. Save the `jdbc-site.xml` file and exit the editor.

gpdb-doc/markdown/pxf/pxfuserimpers.html.md.erb

@@ -96,7 +96,7 @@ PXF user impersonation is enabled by default for Hadoop servers. You can configu
     <property>
         <name>pxf.service.user.impersonation</name>
         <value>true</value>
-    </propery>
+    </property>
     ```
 
 3. If you enabled user impersonation, you must configure Hadoop proxying as described in [Configure Hadoop Proxying](#hadoop). You must also configure [Hive User Impersonation](#hive) and [HBase User Impersonation](#hbase) if you plan to use those services.