remove the unsolicited TAB in README.md

Author: eulerkochy

README.md

@@ -31,7 +31,7 @@ This package implements a variety of data structures, including
 -   SparseIntSet
 -   DiBitVector (in which each element can store two bits)
 -   Red Black Tree
--	  AVL Tree
+-   AVL Tree
 
 Resources
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