How do I remove the top boundary line that above the horizontal arrow line

Question

I would like to remove the top boundary line that is displayed above the horizontal arrow line in a seaborn plot. Currently, the plot includes an arrow line, and there is a visible boundary line positioned above it. I would like to eliminate this top boundary line.

import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt
from matplotlib.patches import FancyArrowPatch

sns.set(style="ticks", font_scale=1.2)

np.random.seed(42)
num_values = 4
data = {
    'TR': [chr(ord('A') + i) for i in range(num_values)],
    'Value': np.random.randint(10, 30, size=num_values)
}
df = pd.DataFrame(data)

fig, ax = plt.subplots(figsize=(5, 7))
i = 'Value'
palette = sns.color_palette("Set1", len(df))

g = sns.barplot(x='TR', y=i, palette=palette, edgecolor="white", errcolor="black", 
                errorbar='sd', zorder=10, data=df) 

ax.set_ylim([0.9*df[i].min(), 1.1*df[i].max()])
sns.despine(ax=ax)


height = 30
bar1 = g.containers[0][0]  
bar2 = g.containers[0][2]  
arrow = FancyArrowPatch((bar1.get_x() + bar1.get_width()/2, height), 
                        (bar2.get_x() + bar2.get_width()/2, height), 
                        arrowstyle='|-|', mutation_scale=10, linewidth=1.5, color='black', 
                        connectionstyle='angle, angleA=90, angleB=0, rad=0')
ax.add_patch(arrow)

plt.tight_layout()
plt.show()

It should resemble the figure shown below.

Answer 1

Inspired by this answer, just plotting the line may be easier than using FancyArrowPatch.

ax.plot([0, 0, 2, 2], [29.5, 30, 30, 29.5], lw=1.5, c='k')