Initial string changes after quoting and unquoting

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### Describe the bug

We were fuzzing yarl url quoting. We assumed that input string shouldn't change after url quotinq and unquoting. But using _quoting_py module input string is not equal to output string after quoting and unquoting. If it's not safe to assume that string will not be changed after quoting and unquoting please let us know.

### To Reproduce

1. Install atheris and yarl 1.18.3:
```
pip install --force-reinstall -v "yarl==1.18.3"
```
2. Run our test `url_quoter_test.py`:
```
from yarl._quoting_py import _Quoter
from yarl._quoting_py import _Unquoter

data = '%%1111'
quote = _Quoter()
unquote = _Unquoter()
text_quoted = quote(data)
text_output = unquote(text_quoted)
assert data == text_output
```
```
python3 url_quoter_fuzz.py crash.raw
```
3. See assertion error that input string is not equal to output string.

### Expected behavior

input string shouldn't change after url quotinq and unquoting

### Logs/tracebacks

```python-traceback
Traceback (most recent call last):
File "/home/fuzzer/fuzz/reproduce.py", line 10, in
assert data == text_output
AssertionError
```

### Python Version

```console
$ python --version
Python 3.9.20
```

### multidict Version

```console
$ python -m pip show multidict
Name: multidict
Version: 6.1.0
Summary: multidict implementation
Home-page: https://github.com/aio-libs/multidict
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache 2
Location: /usr/local/lib64/python3/site-packages
Requires: typing-extensions
Required-by: yarl
```

### propcache Version

```console
$ python -m pip show propcache
Name: propcache
Version: 0.3.0
Summary: Accelerated property cache
Home-page: https://github.com/aio-libs/propcache
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache-2.0
Location: /usr/local/lib64/python3/site-packages
Requires:
Required-by: yarl
```

### yarl Version

```console
$ python -m pip show yarl
Name: yarl
Version: 1.18.3
Summary: Yet another URL library
Home-page: https://github.com/aio-libs/yarl
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache-2.0
Location: /usr/local/lib64/python3/site-packages
Requires: idna, multidict, propcache
Required-by:
```

### OS

alt:p10

### Additional context

We have found it by fuzzing `yarl` with `atheris`. So you can see the full fuzz test:
```
import atheris
import sys

with atheris.instrument_imports():
from yarl._quoting_py import _Quoter
from yarl._quoting_py import _Unquoter

def TestOneInput(input_bytes):
fdp = atheris.FuzzedDataProvider(input_bytes)
data = fdp.ConsumeUnicodeNoSurrogates(sys.maxsize)
print(data)
try:
quote = _Quoter()
unquote = _Unquoter()
text_quoted = quote(data)
text_output = unquote(text_quoted)
assert data == text_output
except ValueError as e:
pass

def main():
atheris.Setup(sys.argv, TestOneInput)
atheris.Fuzz()

if __name__ == "__main__":
main()
```