Remove duplicate words in comments

A few comments contained duplicate "the" in sentences, fix by removing
one occurrence.

Author: Vignesh C <vignesh21@gmail.com>
Discussion: https://postgr.es/m/CALDaNm2aEEiPwGJmPdzBxROVvs8n75yCjKz4K1f1B2TdWpzxTA@mail.gmail.com

Author: danielgustafsson

src/backend/executor/execExprInterp.c

@@ -4686,9 +4686,9 @@ ExecEvalJsonCoercion(ExprState *state, ExprEvalStep *op,
 
 	/*
 	 * Prepare to call json_populate_type() to coerce the boolean result of
-	 * JSON_EXISTS_OP to the target type.  If the the target type is integer
-	 * or a domain over integer, call the boolean-to-integer cast function
-	 * instead, because the integer's input function (which is what
+	 * JSON_EXISTS_OP to the target type.  If the target type is integer or a
+	 * domain over integer, call the boolean-to-integer cast function instead,
+	 * because the integer's input function (which is what
 	 * json_populate_type() calls to coerce to scalar target types) doesn't
 	 * accept boolean literals as valid input.  We only have a special case
 	 * for integer and domains thereof as it seems common to use those types

src/backend/executor/nodeBitmapHeapscan.c

@@ -281,7 +281,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
 			break;
 
 		/*
-		 * If serial, we can error out if the the prefetch block doesn't stay
+		 * If serial, we can error out if the prefetch block doesn't stay
 		 * ahead of the current block.
 		 */
 		if (node->pstate == NULL &&

src/backend/optimizer/prep/prepjointree.c

@@ -293,7 +293,7 @@ transform_MERGE_to_join(Query *parse)
 	 * join (in the ModifyTable node) to distinguish between the MATCHED and
 	 * NOT MATCHED BY SOURCE cases -- see ExecMergeMatched().  Note that this
 	 * creates a modified copy of the join condition, for use above the join,
-	 * without modifying the the original join condition, inside the join.
+	 * without modifying the original join condition, inside the join.
 	 */
 	if (jointype == JOIN_LEFT || jointype == JOIN_FULL)
 	{

src/backend/postmaster/postmaster.c

@@ -3145,7 +3145,7 @@ LaunchMissingBackgroundProcesses(void)
 	 * The checkpointer and the background writer are active from the start,
 	 * until shutdown is initiated.
 	 *
-	 * (If the checkpointer is not running when we enter the the PM_SHUTDOWN
+	 * (If the checkpointer is not running when we enter the PM_SHUTDOWN
 	 * state, it is launched one more time to perform the shutdown checkpoint.
 	 * That's done in PostmasterStateMachine(), not here.)
 	 */