Fix warning on code-block directives

An argument is mandatory for the `code-block` directives.

docs/glances-doc.rst

@@ -349,7 +349,7 @@ Each plugin and export module can have a section.
 
 Example for the CPU plugin:
 
-.. code-block::
+.. code-block:: ini
 
     [cpu]
     user_careful=50
@@ -368,7 +368,7 @@ Example for the CPU plugin:
 By default the ``steal`` CPU time alerts aren't logged. If you want to
 enable log/alert, just add:
 
-.. code-block::
+.. code-block:: ini
 
     steal_log=True
 
@@ -778,7 +778,7 @@ By ``action``, we mean all shell command line. For example, if you want
 to execute the ``foo.py`` script if the last 5 minutes load are critical
 then add the action line to the Glances configuration file:
 
-.. code-block::
+.. code-block:: ini
 
     [load]
     critical=5.0
@@ -788,7 +788,7 @@ All the stats are available in the command line through the use of the
 ``{{mustache}}`` syntax. Another example would be to create a log file
 containing used vs total disk space if a space trigger warning is reached:
 
-.. code-block::
+.. code-block:: ini
 
     [fs]
     warning=70
@@ -821,7 +821,7 @@ You can export statistics to an ``InfluxDB`` server (time series server).
 The connection should be defined in the Glances configuration file as
 following:
 
-.. code-block::
+.. code-block:: ini
 
     [influxdb]
     host=localhost
@@ -840,7 +840,7 @@ InfluxDB 0.9.x or higher also supports an optional tags
 configuration parameter specified as comma separated, key:value pairs.
 For example:
 
-.. code-block::
+.. code-block:: ini
 
     [influxdb]
     host=localhost
@@ -863,7 +863,7 @@ You can export statistics to an ``OpenTSDB`` server (time series server).
 The connection should be defined in the Glances configuration file as
 following:
 
-.. code-block::
+.. code-block:: ini
 
     [opentsdb]
     host=localhost
@@ -884,7 +884,7 @@ You can export statistics to a ``Statsd`` server (welcome to Graphite!).
 The connection should be defined in the Glances configuration file as
 following:
 
-.. code-block::
+.. code-block:: ini
 
     [statsd]
     host=localhost
@@ -901,7 +901,7 @@ and run Glances with:
 
 Glances will generate stats as:
 
-.. code-block::
+.. code-block:: text
 
     'glances.cpu.user': 12.5,
     'glances.cpu.total': 14.9,
@@ -916,7 +916,7 @@ You can export statistics to an ``RabbitMQ`` server (AMQP Broker).
 The connection should be defined in the Glances configuration file as
 following:
 
-.. code-block::
+.. code-block:: ini
 
     [rabbitmq]
     host=localhost