fix typo to make sphinx happy

source/Control_Flow_Statements.rst

@@ -110,6 +110,7 @@ Then create the following two DNA fragments::
    aattccatttactggccagggtaagagttttggtaaatatatagtgatatctggcttg"""
 
 * In a file <my_file.py>
+
 #. Create a function *one_line_dna* that transforms a multi-line sequence into a single-line DNA sequence.
 #. Create a collection containing all enzymes
 #. Create a function that takes two parameters: