Fix temp data cleanup in test_text.py (#10524)

Noticed that when running pytests, cuDF was leaving a temporary file used for a specific test in the testing data folder without removing it. I think  our tests mostly write to `tmp` to avoid this issue.

In switching it to point to `tmp` I noticed the intended data is not being actually written to the file, instead it was writing the string `__repr__` of the generator. I also shrunk the data size by many orders of magnitude, because in the intended case where the data is meant to be truly generated, 30 mil ends up being a little cumbersome and slow.

Authors:
  - https://github.com/brandon-b-miller

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: #10524

python/cudf/cudf/tests/test_text.py

@@ -822,10 +822,10 @@ def test_read_text_byte_range(datadir):
     assert_eq(expected, actual)
 
 
-def test_read_text_byte_range_large(datadir):
-    content = str(("\n" if x % 5 == 0 else "x") for x in range(0, 300000000))
+def test_read_text_byte_range_large(tmpdir):
+    content = str([["\n" if x % 5 == 0 else "x"] for x in range(0, 3000)])
     delimiter = "1."
-    temp_file = str(datadir) + "/temp.txt"
+    temp_file = str(tmpdir) + "/temp.txt"
 
     with open(temp_file, "w") as f:
         f.write(content)