Fix tabs -> spaces.

Author: relistan

docs/source/config/inputs/docker_log.rst

@@ -56,7 +56,7 @@ Config:
 
 - fields_from_labels (array[string], optional):
     A list of labels to pull is as fields. These are pulled in last and will
-	override any fields added from fields_from_env.
+    override any fields added from fields_from_env.
 - since_path (string, optional):
     Path to file where input will write a record of the "since" time for each
     container to be able to not miss log records while Heka is down (see
@@ -74,16 +74,16 @@ Config:
     since Heka has started will be re-fetched.
 - container_expiry_days (int, optional):
     The number of days after which to remove unseen containers from the sinces
-	file. Defaults to 30 days. This prevents containers from building up
-	in the file forever. It has the effect of replaying logs from any container
-	which was not seen for this interval but then re-appears. Containers are
-	tracked by container ID.
+    file. Defaults to 30 days. This prevents containers from building up
+    in the file forever. It has the effect of replaying logs from any container
+    which was not seen for this interval but then re-appears. Containers are
+    tracked by container ID.
 - new_containers_replay_logs (bool, optional):
     Will newly discovered containers replay all of the logs currently available
-	via the Docker logs endpoint? Defaults to true. If you are upgrading from
-	a previous version of heka, you may want to consider setting this to false
-	when first upgrading to prevent the massive replay of logs from all of
-	your existing containers.
+    via the Docker logs endpoint? Defaults to true. If you are upgrading from
+    a previous version of heka, you may want to consider setting this to false
+    when first upgrading to prevent the massive replay of logs from all of
+    your existing containers.
 
 Example: