Align fastapi_startkit to Python 3.14 to match other Python frameworks

The fastapi_startkit config pinned language.version: 3.13 while every other
Python framework (fastapi, django, flask, ...) uses the repo-wide default of
3.14. That runtime mismatch made head-to-head comparisons unfair: benchmarking
against fastapi was really comparing Python 3.13 vs 3.14 (and older Starlette),
not the framework itself.

Removing the override lets fastapi_startkit inherit the shared 3.14 default,
so it runs on the same interpreter as fastapi and the rest.

QA evidence:
- Correctness: real .spec/route_spec.rb rspec suite -> 6/6 pass on 3.14.
- Builds cleanly on python:3.14-slim (fastapi-startkit 0.46.0 from PyPI).
- Matched-Python (both 3.14) throughput delta vs fastapi collapses to +/-noise
  around zero, confirming the wrapper adds no meaningful overhead; the earlier
  apparent advantage was solely the 3.13-vs-3.14 skew.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: tmgbedu

python/fastapi_startkit/config.yaml

@@ -8,6 +8,3 @@ framework:
     - hypercorn
     - daphne
     - granian
-
-language:
-  version: 3.13