fix title underlines

Author: Chris Cho

source/kafka-sink-postprocessors.txt

@@ -191,7 +191,7 @@ setting.
 .. _config-blocklist-allowlist:
 
 Block List / Allow List Projector
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 This section provides example projection configurations to show how they
 filter the following sample record:
@@ -236,7 +236,7 @@ filter the following sample record:
 .. _blocklist-example:
 
 Block List Projection Example
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 In the following example sink configuration, we specify a block list
 projection and the specific fields to omit from the record:
@@ -284,7 +284,7 @@ The record contains the following data after applying the projection:
 .. _allowlist-example:
 
 Allow List Projection Example
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 In the following example sink configuration, we specify an allow list
 projection and the specific fields to include in the record: