Remove unused code to fix coverage

- Remove unused is_pydantic_v2_11() function and _is_v2_11 variable
- Simplify chain_as_tuple by removing unused n==0 and n==1 optimizations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: koxudaxi

src/datamodel_code_generator/types.py

@@ -180,14 +180,9 @@ def validate(cls, v: Any) -> UnionIntFloat:
 def chain_as_tuple(*iterables: Iterable[T]) -> tuple[T, ...]:
     """Chain multiple iterables and return as a tuple.
 
-    Optimized for common cases with 0-2 iterables to avoid chain() overhead.
+    Optimized for the common case of 2 iterables to avoid chain() overhead.
     """
-    n = len(iterables)
-    if n == 0:  # pragma: no cover
-        return ()
-    if n == 1:  # pragma: no cover
-        return tuple(iterables[0])
-    if n == 2:  # noqa: PLR2004
+    if len(iterables) == 2:  # noqa: PLR2004
         return (*iterables[0], *iterables[1])
     return tuple(chain(*iterables))
 

src/datamodel_code_generator/util.py

@@ -47,7 +47,6 @@ def get_pydantic_version() -> tuple[Any, bool, bool]:
 
 
 _is_v2: bool | None = None
-_is_v2_11: bool | None = None
 
 
 def is_pydantic_v2() -> bool:
@@ -58,14 +57,6 @@ def is_pydantic_v2() -> bool:
     return _is_v2
 
 
-def is_pydantic_v2_11() -> bool:
-    """Check if pydantic v2.11+ is installed."""
-    global _is_v2_11  # noqa: PLW0603
-    if _is_v2_11 is None:  # pragma: no branch
-        _is_v2_11 = get_pydantic_version()[2]
-    return _is_v2_11
-
-
 _YAML_1_2_BOOL_PATTERN = re.compile(r"^(?:true|false|True|False|TRUE|FALSE)$")
 _YAML_DEPRECATED_BOOL_VALUES = {"True", "False", "TRUE", "FALSE"}