BUG: guess_datetime_format doesn't guess format correctly for UTC+1
- [x] closes #48921 (Replace xxxx with the Github issue number)
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Haven't added a whatsnew note as this function isn't (yet) user-facing

This extra try-except adds about 9 microseconds on my laptop:

upstream/main:
```
In [2]: %%timeit
   ...: guess_datetime_format('2020-01-01 00:00:00 UTC+1')
   ...: 
   ...: 
93 µs ± 652 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)
```
this branch:
```
In [3]: %%timeit
   ...: guess_datetime_format('2020-01-01 00:00:00 UTC+1')
   ...: 
   ...: 
102 µs ± 141 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)
```
IMO this is negligible and worth it
Thanks @MarcoGorelli 