Re: Remove an obsolete comment in gistinsert()

Hi Tender,

> While learning the GIST codes, I find an obsolete comment in gistinsert ().
>
> itup = gistFormTuple(giststate, r,
>                                   values, isnull, true /* size is currently bogus */ );

Thanks for reporting. I agree that this is an oversight of commit 1f7ef54.

The commit changed the signature of gistFormTuple():

```
 IndexTuple
 gistFormTuple(GISTSTATE *giststate, Relation r,
-                         Datum attdata[], int datumsize[], bool isnull[])
+                         Datum attdata[], bool isnull[], bool newValues)
```

... but left the comment for the `datumsize` argument:

```
        itup = gistFormTuple(&buildstate->giststate, index,
-               values, NULL /* size is currently bogus */, isnull);
+               values, isnull, true /* size is currently bogus */);
```

I checked the rest of gistFormTuple() calls and also looked for other
comments like this. There seems to be only one call like this to fix.