I found the solution, I tried to add dotted grid lines on the dashboard and again selected none for GridLines and voila it's gone.
Thank you so much for your immediate response, Zhouyi Zhang!!
Hi Akanksha Sinha;
Please don't forget to mark ZZ's answer as "Correct" to close out the question; this also lets other people see the solution immediately.
It's a matter of opinion, you might want to reconsider your graph type for this viz.
Currently, you're asking your viewer to look across five bars to make a year-on-year comparison. For me and my old eyes, this can be confusing!
A better choice might be alternating bars:
Or a simple line graph:
The benefits could be based on how your viewer wants to explore the data:
Here Trend within Country is when a viewer is only interested in looking at one country across a time period.
Comparative Trend is viewing how each country stacks up against the other over time.
Again, this is my personal opinion.
All the best!