Multiplex doc: attempt to reduce confusion on file format and line numbers

Ideally our HTML formatted docs would have toggable line numbers. Since
we don't have that, let's just try to be clearer about the line numbers
not being part of the multiplex file format.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

docs/source/MultiplexConfig.rst

@@ -13,36 +13,38 @@ file is the visible separation of different scopes. Even very advanced setups
 are still human readable, unlike traditional sparse, multi-dimensional-matrices
 of parameters.
 
-Let's start with an example (line numbers added at the beginning)::
-
-     1    hw:
-     2        cpu: !mux
-     3            intel:
-     4                cpu_CFLAGS: '-march=core2'
-     5            amd:
-     6                cpu_CFLAGS: '-march=athlon64'
-     7            arm:
-     8                cpu_CFLAGS: '-mabi=apcs-gnu -march=armv8-a -mtune=arm8'
-     9        disk: !mux
-    10            scsi:
-    11                disk_type: 'scsi'
-    12            virtio:
-    13                disk_type: 'virtio'
-    14    distro: !mux
-    15        fedora:
-    16            init: 'systemd'
-    17        mint:
-    18            init: 'systemv'
-    19    env: !mux
-    20        debug:
-    21            opt_CFLAGS: '-O0 -g'
-    22        prod:
-    23            opt_CFLAGS: '-O2'
-
-
-There are couple of key=>value pairs (4,6,8,11,13,...) and there are
-named nodes which define scope (1,2,3,5,7,9,...). There are also additional
-flags (2, 9, 14, 19) which modifies the behavior.
+Let's start with an example (line numbers at the first columns are for
+documentation purposes only, they are not part of the multiplex file
+format)::
+
+     1  hw:
+     2      cpu: !mux
+     3          intel:
+     4              cpu_CFLAGS: '-march=core2'
+     5          amd:
+     6              cpu_CFLAGS: '-march=athlon64'
+     7          arm:
+     8              cpu_CFLAGS: '-mabi=apcs-gnu -march=armv8-a -mtune=arm8'
+     9      disk: !mux
+    10          scsi:
+    11              disk_type: 'scsi'
+    12          virtio:
+    13              disk_type: 'virtio'
+    14  distro: !mux
+    15      fedora:
+    16          init: 'systemd'
+    17      mint:
+    18          init: 'systemv'
+    19  env: !mux
+    20      debug:
+    21          opt_CFLAGS: '-O0 -g'
+    22      prod:
+    23          opt_CFLAGS: '-O2'
+
+
+There are couple of key=>value pairs (lines 4,6,8,11,13,...) and there are
+named nodes which define scope (lines 1,2,3,5,7,9,...). There are also additional
+flags (lines 2, 9, 14, 19) which modifies the behavior.
 
 
 Nodes