ensure we don't say 'insure' when we mean 'ensure'

jstests/replsets/capped_id.js

@@ -125,7 +125,7 @@ for( testnum=0; testnum < numtests; testnum++ ){
     slave2db.system.indexes.find().forEach(printjson);
     print("");
 
-    // insure all nodes have _id index
+    // ensure all nodes have _id index
     assert.eq( 1 ,
                masterdb.system.indexes.find( { key:{"_id" : 1}, ns: dbname + "." + coll } ).count() ,
                "master has an _id index on capped collection");

jstests/slowNightly/ttl_sharded.js

@@ -40,7 +40,7 @@ assert.soon(
     }, "TTL index on x didn't delete enough" , 70 * 1000
 );
 
-// insure that count ultimately ends up at 6
+// ensure that count ultimately ends up at 6
 assert.eq( 0 , t.find( { x : { $lt : new Date( now - 20000000 ) } } ).count() );
 assert.eq( 6 , t.count() );
 

jstests/use_power_of_2.js

@@ -1,4 +1,4 @@
-/* This test insures that the usePowerOf2 user flag
+/* This test ensures that the usePowerOf2 user flag
  * effectively reuses space. The test repeatedly inserts and
  * then deletes a batch of variable-length strings, then checks
  * that doing so does not cause the storageSize to grow. */

src/mongo/db/hashindex.cpp

@@ -95,7 +95,7 @@ namespace mongo {
         const vector<FieldInterval>& intervals = frs.range( _hashedField.c_str() ).intervals();
 
         //Force a match of the query against the actual document by giving
-        //the cursor a matcher with an empty indexKeyPattern.  This insures the
+        //the cursor a matcher with an empty indexKeyPattern.  This ensures the
         //index is not used as a covered index.
         //NOTE: this forcing is necessary due to potential hash collisions
         const shared_ptr< CoveredIndexMatcher > forceDocMatcher(