absurlreplacer: remove superfluous code

absurlreplacer: remove superfluous code

```
benchmark                    old ns/op     new ns/op     delta
BenchmarkAbsURL              18381         17946         -2.37%
BenchmarkAbsURLSrcset        19531         19236         -1.51%
BenchmarkXMLAbsURLSrcset     19316         19046         -1.40%
BenchmarkXMLAbsURL           9818          9561          -2.62%

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        2354          2374          +0.85%
BenchmarkXMLAbsURLSrcset     2584          2574          -0.39%
BenchmarkXMLAbsURL           1864          1871          +0.38%
```

See #1059