feat(python): set default languge to python for pyfory (#2490)

<!--
**Thanks for contributing to Fory.**

**If this is your first time opening a PR on fory, you can refer to
[CONTRIBUTING.md](https://github.com/apache/fory/blob/main/CONTRIBUTING.md).**

Contribution Checklist

- The **Apache Fory** community has requirements on the naming of pr
titles. You can also find instructions in
[CONTRIBUTING.md](https://github.com/apache/fory/blob/main/CONTRIBUTING.md).

- Fory has a strong focus on performance. If the PR you submit will have
an impact on performance, please benchmark it first and provide the
benchmark result here.
-->

## What does this PR do?

<!-- Describe the purpose of this PR. -->

## Related issues

<!--
Is there any related issue? Please attach here.

- #xxxx0
- #xxxx1
- #xxxx2
-->

## Does this PR introduce any user-facing change?

<!--
If any user-facing interface changes, please [open an
issue](https://github.com/apache/fory/issues/new/choose) describing the
need to do so and update the document if necessary.
-->

- [ ] Does this PR introduce any public API change?
- [ ] Does this PR introduce any binary protocol compatibility change?

## Benchmark

<!--
When the PR has an impact on performance (if you don't know whether the
PR will have an impact on performance, you can submit the PR first, and
if it will have impact on performance, the code reviewer will explain
it), be sure to attach a benchmark data here.
-->

Author: chaokunyang

python/pyfory/_fory.py

@@ -117,7 +117,7 @@ class Fory:
 
     def __init__(
         self,
-        language=Language.XLANG,
+        language=Language.PYTHON,
         ref_tracking: bool = False,
         require_type_registration: bool = True,
     ):

python/pyfory/_serialization.pyx

@@ -602,7 +602,7 @@ cdef class Fory:
 
     def __init__(
             self,
-            language=Language.XLANG,
+            language=Language.PYTHON,
             ref_tracking: bool = False,
             require_type_registration: bool = True,
     ):