Can't resize (FileVault) partition after Bootcamp removal

As @alan-shutko pointed out with a hyperlink, the only way to resize a encrypted partition is to disable encryption, (rebooting again,) then changing the size. It worked for me!

It's a lengthy process if you wait for it, but bearable if you let the decryption happen overnight.

An alternative to the disabling encryption is to use command diskutil cs resizeStack

The details on how it works has been documented by Klanomath here

One thing I wanted to add is that it also works with FileVault. I have tried and the performance was pretty good. It took me 5-8 minutes to resize the 230GB partition to 250GB.

To sum it up:

Firstly: Boot from a separate system such as USB or the internet

Secondly: use this command diskutil cs list to get the volume Id of the Logical Volume partition

I.e:

        $ diskutil cs list
    CoreStorage logical volume groups (1 found)
    |
    +-- Logical Volume Group A061B44A-9E3D-41B1-8943-C11BD76DDE37
        =========================================================
        Name:         Macintosh HD
        Status:       Online
        Size:         250337738752 B (250.3 GB)
        Free Space:   180224 B (180.2 KB)
        |
        +-< Physical Volume 01F57DD6-2209-4FA6-A085-93C36C36B3D4
        |   ----------------------------------------------------
        |   Index:    0
        |   Disk:     disk0s2
        |   Status:   Online
        |   Size:     250337738752 B (250.3 GB)
        |
        +-> Logical Volume Family 777A289D-71C0-43A2-9C10-39EFEE313964
            ----------------------------------------------------------
            Encryption Status:       Unlocked
            Encryption Type:         AES-XTS
            Conversion Status:       Complete
            Conversion Direction:    -none-
            Has Encrypted Extents:   Yes
            Fully Secure:            Yes
            Passphrase Required:     Yes
            |
            +-> Logical Volume 11F03152-0861-4BA0-AA78-1F1D8CE520AF
                ---------------------------------------------------
                Disk:                  disk1
                Status:                Online
                Size (Total):          249999917056 B (250.0 GB)
                Conversion Progress:   -none-
                Revertible:            Yes (unlock and decryption required)
                LV Name:               Macintosh HD
                Volume Name:           Macintosh HD
                Content Hint:          Apple_HFS

It is 11F03152-0861-4BA0-AA78-1F1D8CE520AF

And you can use this command to resize:

diskutil cs resizeStack 11F03152-0861-4BA0-AA78-1F1D8CE520AF 250g