DOC: fix RT03, ES01 for pandas.core.resample.Resampler.ffill (#59871)

Author: tuhinsharma121

ci/code_checks.sh

@@ -155,7 +155,6 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
         -i "pandas.core.groupby.SeriesGroupBy.plot PR02" \
         -i "pandas.core.groupby.SeriesGroupBy.sem SA01" \
         -i "pandas.core.resample.Resampler.__iter__ RT03,SA01" \
-        -i "pandas.core.resample.Resampler.ffill RT03" \
         -i "pandas.core.resample.Resampler.get_group RT03,SA01" \
         -i "pandas.core.resample.Resampler.groups SA01" \
         -i "pandas.core.resample.Resampler.indices SA01" \

pandas/core/resample.py

@@ -529,14 +529,20 @@ def ffill(self, limit: int | None = None):
         """
         Forward fill the values.
 
+        This method fills missing values by propagating the last valid
+        observation forward, up to the next valid observation. It is commonly
+        used in time series analysis when resampling data to a higher frequency
+        (upsampling) and filling gaps in the resampled output.
+
         Parameters
         ----------
         limit : int, optional
             Limit of how many values to fill.
 
         Returns
         -------
-        An upsampled Series.
+        Series
+            The resampled data with missing values filled forward.
 
         See Also
         --------