DOCS: Clarify PTR example (#2792)

Author: tlimoncelli

documentation/functions/domain/PTR.md

@@ -48,9 +48,9 @@ then the name will be replaced with `4.3`.  Note that the output
 of `REV("1.2.3.4")` is `4.3.2.1.in-addr.arpa.`, which means the following
 are all equivalent:
 
-* `PTR(REV("1.2.3.4"), `
-* `PTR("4.3.2.1.in-addr.arpa."), `
-* `PTR("4.3",`    // Assuming the domain is `2.1.in-addr.arpa`
+* `PTR(REV("1.2.3.4", ...`
+* `PTR("4.3.2.1.in-addr.arpa.", ...`
+* `PTR("4.3", ...`    // Assuming the domain is `2.1.in-addr.arpa`
 
 All magic is RFC2317-aware. We use the first format listed in the
 RFC for both [`REV()`](../global/REV.md) and `PTR()`. The format is