Problems after deleting Bootcamp Partion/EFI I am running High Sierra 10.13.6 on a MacBook Pro.

To cut a long story short, I installed a release of Windows 10 on my Mac and did not like it. So I decided to delete it.

I did my best to remove Windows by using the Disk Utility to delete the partition, but problems arose when the Mac would restart. The Mac would automatically boot into recovery mode in Windows. I would have to shut the computer down, then power up while holding down the optionkey until I could select the Mac Drive. I researched a bit more and found this could be fixed by mounting the EFI volume on /dev/disk0s1 and deleting the Windows and Boot folders inside the EFI folder. So, this left just the the APPLE folder. After following these steps and restarted the computer, I was greeted with a flashing grey folder with a question mark on it. So, I restarted with option key held down, then chose the only drive, the Mac drive. 

I ran the diskutil list command. The output is shown below.

/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         121.3 GB   disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         120.1 GB   disk0s2
   3:           Windows Recovery                         901.8 MB   disk0s3

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +120.1 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD            66.7 GB    disk1s1
   2:                APFS Volume Preboot                 22.0 MB    disk1s2
   3:                APFS Volume Recovery                515.0 MB   disk1s3
   4:                APFS Volume VM                      1.1 GB     disk1s4


Now, I think I made the mistake by deleting the Boot folder, but I am not sure. So,  Also, as an aside question: As previously stated, I have deleted everything regarding Windows, so why is the line below appearing?

   3:           Windows Recovery                         901.8 MB   disk0s3


If anyone could help me, it would greatly appreciated.
Quote from OP:


  Now, I think I made the mistake by deleting the Boot folder, but I am not sure. 


My response:

You were correct to remove the Boot folder. 

Quote from OP:


  I would have to shut the computer down, then power up while holding down the option key until I could select the Mac Drive.


My response:

You should have held down the control key before choosing the Mac drive. This will make macOS the default operating system went starting up.

Quote from OP:


  As previously stated, I have deleted everything regarding Windows, so why is the line below appearing?


3:           Windows Recovery                         901.8 MB   disk0s3


My response:

This is part of Windows. You should remove this partition and add the space back to the APFS container. The commands to do this are given below.

diskutil eraseVolume free none disk0s3
diskutil apfs resizeContainer disk0s2 0