You can get what handles/labels should exist in the legend before you actually draw the legend itself. You then draw the legend only with the specific ones you want.
import matplotlib.pyplot as plt
import seaborn as sns
import pandas as pd
tips = sns.load_dataset("tips")
sns.stripplot(x="day", y="total_bill", hue="smoker", data=tips, jitter=True, palette="Set2", dodge=True, linewidth=1, edgecolor="gray")
# Get the ax object to use later.
ax = sns.boxplot(x="day", y="total_bill", hue="smoker", data=tips, palette="Set2", fliersize=0)
# Get the handles and labels. For this example it'll be 2 tuples
# of length 4 each.
handles, labels = ax.get_legend_handles_labels()
# When creating the legend, only use the first two elements
# to effectively remove the last two.
l = plt.legend(handles[0:2], labels[0:2], bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0.)
