Remove stale CSV rejection snippet

Removes a RustPython-only assertion that contradicts the
CPython-compatible dialect validation added by this branch.

Scope: test-only
AI-Assisted-By: Codex

extra_tests/snippets/stdlib_csv.py

@@ -1,6 +1,5 @@
 import csv
 import io
-import sys
 
 from testutils import assert_raises
 
@@ -263,42 +262,6 @@ def test_multichar_lineterminator():
 test_multichar_lineterminator()
 
 
-def test_reject_non_ascii_lineterminator():
-    # CPython accepts non-ASCII line terminators; RustPython rejects them
-    # because the writer quotes and escapes byte by byte. Supporting them
-    # requires code-point-wise handling as part of full Unicode dialect support.
-    with assert_raises(csv.Error):
-        csv.writer(io.StringIO(), lineterminator="é")
-
-    with assert_raises(csv.Error):
-        csv.writer(io.StringIO(), lineterminator="\x85")
-
-    with assert_raises(csv.Error):
-        csv.writer(io.StringIO(), lineterminator="\ud800")
-
-    with assert_raises(csv.Error):
-        csv.writer(
-            io.StringIO(), lineterminator="é", quoting=csv.QUOTE_NONE, escapechar="\\"
-        )
-
-    with assert_raises(csv.Error):
-        csv.register_dialect("non_ascii_lt", lineterminator="é")
-
-    class NonAsciiDialect(csv.excel):
-        lineterminator = "é"
-
-    with assert_raises(csv.Error):
-        NonAsciiDialect()
-
-    buf = io.StringIO()
-    csv.writer(buf, lineterminator="!@#").writerow(["a", "b"])
-    assert buf.getvalue() == "a,b!@#"
-
-
-if sys.implementation.name == "rustpython":
-    test_reject_non_ascii_lineterminator()
-
-
 def test_empty_lineterminator():
     class EmptyLineTerminator(csv.excel):
         lineterminator = ""