chore(subprocess) Fix ruff issues

uv run ruff check --select ALL . --fix --unsafe-fixes --preview --show-fixes; uv run ruff format .

Fixed 6 errors:
- src/libvcs/_internal/subprocess.py:
    3 × PYI061 (redundant-none-literal)
    3 × UP045 (non-pep604-annotation-optional)

Author: tony

src/libvcs/_internal/subprocess.py

@@ -258,7 +258,7 @@ def Popen(
         args: _CMD | None = ...,
         universal_newlines: t.Literal[False] = ...,
         *,
-        text: t.Literal[None, False] = ...,
+        text: t.Literal[False] | None = ...,
         encoding: None = ...,
         errors: None = ...,
     ) -> subprocess.Popen[bytes]: ...
@@ -370,7 +370,7 @@ def check_output(
         input: str | bytes | None = ...,
         encoding: None = ...,
         errors: None = ...,
-        text: t.Literal[None, False] = ...,
+        text: t.Literal[False] | None = ...,
         **kwargs: t.Any,
     ) -> bytes: ...
 
@@ -484,7 +484,7 @@ def run(
         encoding: None = ...,
         errors: None = ...,
         input: bytes | None = ...,
-        text: t.Literal[None, False] = ...,
+        text: t.Literal[False] | None = ...,
     ) -> subprocess.CompletedProcess[bytes]: ...
 
     def run(