fix read_csv to work with different overloads

[Dr-Irv]

pylance 2022.2.0

The following code reports errors incorrectly:

from io import StringIO
import pandas as pd
from pandas.io.parsers import TextFileReader

dio = StringIO("a,b\n 1,2\n 3,4\n")

df: pd.DataFrame = pd.read_csv(dio)

print(df)

dio.seek(0)
tr: pd.DataFrame = pd.read_csv(dio)

dio.seek(0)
tr2: TextFileReader = pd.read_csv(dio, iterator=True)

dio.seek(0)
tr3: pd.DataFrame = pd.read_csv(dio, iterator=False)

dio.seek(0)
tr5: TextFileReader = pd.read_csv(dio, chunksize=10)

dio.seek(0)
tr6: pd.DataFrame = pd.read_csv(dio, chunksize=None)

dio.seek(0)
tr7: pd.DataFrame = pd.read_csv(dio, header="infer")

dio.seek(0)
tr8: TextFileReader = pd.read_csv(dio, header="infer", iterator=True)


ftr1: TextFileReader = pd.read_csv("hey.csv")
ftr2: pd.DataFrame = pd.read_csv("hey.csv", iterator=True)
ftr3: TextFileReader = pd.read_csv("hey.csv", iterator=False)
ftr5: pd.DataFrame = pd.read_csv("hey.csv", chunksize=10)
ftr6: TextFileReader = pd.read_csv("he.csv", chunksize=None)
ftr7: TextFileReader = pd.read_csv("hey.csv", header="infer")
ftr8: pd.DataFrame = pd.read_csv("hey.csv", header="infer", iterator=True)

e.g., on the first assignment of tr1:

Expression of type "TextFileReader" cannot be assigned to declared type "DataFrame"
  "TextFileReader" is incompatible with "DataFrame"

The test code above is set up to pass on all the assignments to tr# and fail on the assignments to ftr#

This was all working with PR #87 and I think #129 messed it up (@gramster)