Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

   pydantic version: 1.9.0
            pydantic compiled: True
                 install path: C:\Program Files\Python310\Lib\site-packages\pydantic
               python version: 3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC v.1929 64 bit (AMD64)]
                     platform: Windows-10-10.0.19044-SP0
     optional deps. installed: ['dotenv', 'typing-extensions']

Code Demonstration bug

from pydantic.json import timedelta_isoformat
from datetime import datetime

timedelta = (datetime.fromisoformat("2022-03-15 08:00:57.152735+00:00") -
             datetime.fromisoformat("2022-03-15 08:00:57.264000+00:00"))

incorrect_iso_string = timedelta_isoformat(timedelta)
# this produce "P-1DT23H59M59.888735S"  and that is incorrect according to documentation ([±]P[DD]DT[HH]H[MM]M[SS]S)
...

i have verified this on two diferent computers with two diferents setups (conda/regular python so it should not be problem of my enviroment)