Modified longest_common_ssubsequence.py for successful doctests (TheAlgorithms#1332)

Author: jpg-130

dynamic_programming/longest_common_subsequence.py

@@ -76,6 +76,7 @@ def longest_common_subsequence(x: str, y: str):
     expected_subseq = "GTAB"
 
     ln, subseq = longest_common_subsequence(a, b)
-    assert expected_ln == ln
-    assert expected_subseq == subseq
-    print("len =", ln, ", sub-sequence =", subseq)
+##    print("len =", ln, ", sub-sequence =", subseq)
+    import doctest
+
+    doctest.testmod()