chore(pandas): use sep instead of deprecated delim_whitespace (#2148)

* delim_whitespace param on read_table() and read_csv() is deprecated, use sep="\\s+" instead
* https://pandas.pydata.org/docs/whatsnew/v2.2.0.html#other-deprecations

Author: wpbonelli

flopy/utils/flopy_io.py

@@ -355,7 +355,7 @@ def loadtxt(
 
     if use_pandas:
         if delimiter.isspace():
-            kwargs["delim_whitespace"] = True
+            kwargs["sep"] = "\\s+"
         if isinstance(dtype, np.dtype) and "names" not in kwargs:
             kwargs["names"] = dtype.names
 

flopy/utils/sfroutputfile.py

@@ -165,7 +165,7 @@ def get_dataframe(self):
         """
         kwargs = {
             "filepath_or_buffer": self.filename,
-            "delim_whitespace": True,
+            "sep": "\\s+",
             "header": None,
             "names": self.names,
             "skiprows": self.sr,