[Docs] Fix typo in LoopTerminology.

llvm/docs/LoopTerminology.rst

@@ -43,7 +43,7 @@ The definition of a loop comes with some additional terminology:
 
 * An **entering block** (or **loop predecessor**) is a non-loop node
   that has an edge into the loop (necessarily the header). If there is
-  only one entering block entering block, and its only edge is to the
+  only one entering block, and its only edge is to the
   header, it is also called the loop's **preheader**. The preheader
   dominates the loop without itself being part of the loop.