On `1.11.0-alpha2`
Old:
```julia
@benchmark Base.dec($0x1, $0, $false)
BenchmarkTools.Trial: 10000 samples with 994 evaluations.
 Range (min … max):  33.702 ns …   4.242 μs  ┊ GC (min … max):  0.00% … 97.61%
 Time  (median):     37.626 ns               ┊ GC (median):     0.00%
 Time  (mean ± σ):   45.787 ns ± 147.794 ns  ┊ GC (mean ± σ):  14.53% ±  4.47%

    ▄▅▆▇█▇▇▅▃▃▂▂▂▁    ▁▂▁▁▁             ▁▁   ▁                 ▂
  ▄▇███████████████▇▇██████▇█▆▆▄▄▃▄▅▄▆▇████████▆▅▅▇▆▅▆▄▄▅▄▄▄▁▅ █
  33.7 ns       Histogram: log(frequency) by time      67.5 ns <

 Memory estimate: 88 bytes, allocs estimate: 3.
```
New:
```julia
BenchmarkTools.Trial: 10000 samples with 995 evaluations.
 Range (min … max):  27.538 ns …   3.397 μs  ┊ GC (min … max):  0.00% … 97.86%
 Time  (median):     30.151 ns               ┊ GC (median):     0.00%
 Time  (mean ± σ):   34.547 ns ± 105.101 ns  ┊ GC (mean ± σ):  10.37% ±  3.39%

       ▁ █▆▃  ▁
  ▂▂▃▃▅█████▆████▆▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂ ▃
  27.5 ns         Histogram: frequency by time         43.8 ns <

 Memory estimate: 56 bytes, allocs estimate: 2.
```


Fixes #53950, actually now even faster than `1.10.2`.

It doesn't look like the length is ever changed and we don't return
these `StringMemory`s so this change should be fine.