Small patch to remove some duplicate words in comments

diff --git a/src/backend/partitioning/partprune.c b/src/backend/partitioning/partprune.c
index 0dd55ac1ba..b5c1c7d4dd 100644
--- a/src/backend/partitioning/partprune.c
+++ b/src/backend/partitioning/partprune.c
@@ -1428,7 +1428,7 @@ gen_prune_steps_from_opexps(PartitionScheme part_scheme,
 					/*
 					 * For each clause for the "last" column, after appending
 					 * the clause's own expression to the 'prefix', we'll
-					 * generate one step using the so generated vector and and
+					 * generate one step using the so generated vector and
 					 * assign = as its strategy.  Actually, 'prefix' might
 					 * contain multiple clauses for the same key, in which
 					 * case, we must generate steps for various combinations
@@ -2828,9 +2828,9 @@ get_matching_range_bounds(PartitionPruneContext *context,
 	}
 
 	/*
-	 * Skip a gap.  See the above comment about how we decide whether or or
-	 * not to scan the default partition based whether the datum that will
-	 * become the maximum datum is finite or not.
+	 * Skip a gap.  See the above comment about how we decide whether or not
+	 * to scan the default partition based whether the datum that will become
+	 * the maximum datum is finite or not.
 	 */
 	if (maxoff >= 1 && partindices[maxoff] < 0)
 	{
diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c
index 3b4a09b1a7..140783cfb3 100644
--- a/src/backend/statistics/dependencies.c
+++ b/src/backend/statistics/dependencies.c
@@ -395,7 +395,7 @@ statext_dependencies_build(int numrows, HeapTuple *rows, Bitmapset *attrs,
 			degree = dependency_degree(numrows, rows, k, dependency, stats, attrs);
 
 			/*
-			 * if the dependency seems entirely invalid, don't store it it
+			 * if the dependency seems entirely invalid, don't store it
 			 */
 			if (degree == 0.0)
 				continue;
diff --git a/src/backend/utils/adt/geo_spgist.c b/src/backend/utils/adt/geo_spgist.c
index 4aff973ef3..f9e8db63dd 100644
--- a/src/backend/utils/adt/geo_spgist.c
+++ b/src/backend/utils/adt/geo_spgist.c
@@ -35,10 +35,10 @@
  *
  * We are using traversal values provided by SP-GiST to calculate and
  * to store the bounds of the quadrants, while traversing into the tree.
- * Traversal value has all the boundaries in the 4D space, and is is
- * capable of transferring the required boundaries to the following
- * traversal values.  In conclusion, three things are necessary
- * to calculate the next traversal value:
+ * Traversal value has all the boundaries in the 4D space, and is capable
+ * of transferring the required boundaries to the following traversal
+ * values.  In conclusion, three things are necessary to calculate the
+ * next traversal value:
  *
  *	(1) the traversal value of the parent
  *	(2) the quadrant of the current node