03-index-slice-subset.md: Fix code blocks and blockquotes

Signed-off-by: Maxim Belkin <[email protected]>

Author: maxim-belkin

_episodes/03-index-slice-subset.md

@@ -279,7 +279,7 @@ which gives the **output**
 1      7   16  1977
 2      7   16  1977
 ~~~
->> {: .output}
+{: .output}
 
 Notice that we asked for a slice from 0:3. This yielded 3 rows of data. When you
 ask for 0:3, you are actually telling Python to start at index 0 and select rows
@@ -328,7 +328,7 @@ gives the **output**
 ~~~
 'F'
 ~~~
->> {: .output}
+{: .output}
 
 Remember that Python indexing begins at 0. So, the index location [2, 6]
 selects the element that is 3 rows down and 7 columns over in the DataFrame.