absurlreplacer: remove superfluous code, take 2

absurlreplacer: remove superfluous code, take 2

 ```
benchmark                    old ns/op     new ns/op     delta
BenchmarkAbsURL              17946         17454         -2.74%
BenchmarkAbsURLSrcset        19236         18979         -1.34%
BenchmarkXMLAbsURLSrcset     19046         18688         -1.88%
BenchmarkXMLAbsURL           9561          9432          -1.35%

benchmark                    old allocs     new allocs     delta
BenchmarkAbsURL              24             24             +0.00%
BenchmarkAbsURLSrcset        29             29             +0.00%
BenchmarkXMLAbsURLSrcset     27             27             +0.00%
BenchmarkXMLAbsURL           12             12             +0.00%

benchmark                    old bytes     new bytes     delta
BenchmarkAbsURL              3139          3139          +0.00%
BenchmarkAbsURLSrcset        2374          2369          -0.21%
BenchmarkXMLAbsURLSrcset     2574          2572          -0.08%
BenchmarkXMLAbsURL           1871          1871          +0.00%

```

See #1059