replace shallowCopy with move, otherwise it fails nimgen

[ringabout]

ref nim-lang/Nim#19972

2022-07-28T11:12:09.4182108Z Downloading https://github.com/nim-lang/c2nim using git
2022-07-28T11:12:09.4182506Z   Verifying dependencies for c2nim@#head
2022-07-28T11:12:09.4182810Z  Installing c2nim@#head
2022-07-28T11:12:09.4183134Z    Building c2nim/c2nim using c backend
2022-07-28T11:12:09.4183913Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/c2nim.nim(12, 16) �[0m�[33mWarning: �[0mNumber of spaces around '/' is not consistent�[36m [Spacing]�[0m�[0m
2022-07-28T11:12:09.4184858Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/llstream.nim(13, 3) �[0m�[33mWarning: �[0mimported and not used: 'strutils'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4186479Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/options.nim(11, 26) �[0m�[33mWarning: �[0mimported and not used: 'osproc'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4187298Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/idents.nim(15, 11) �[0m�[33mWarning: �[0mimported and not used: 'strutils'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4188112Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/ast.nim(13, 41) �[0m�[33mWarning: �[0mimported and not used: 'strutils'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4188892Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/ast.nim(13, 55) �[0m�[33mWarning: �[0mimported and not used: 'sha1'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4189688Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/ast.nim(13, 22) �[0m�[33mWarning: �[0mimported and not used: 'nversion'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4190486Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/ast.nim(13, 32) �[0m�[33mWarning: �[0mimported and not used: 'options'�[36m [UnusedImport]�[0m�[0m
2022-07-28T11:12:09.4191223Z �[1m/tmp/nimble_20270/githubcom_nimlangc2nim_#head/compiler/msgs.nim(190, 3) �[0m�[31mError: �[0mundeclared identifier: 'shallowCopy'
2022-07-28T11:12:09.4191761Z candidates (edit distance, scope distance); see '--spellSuggest': 
2022-07-28T11:12:09.4192264Z  (4, 4): 'shallow' [proc declared in /home/runner/work/Nim/Nim/lib/system.nim(2799, 6)]
2022-07-28T11:12:09.4192788Z  (4, 4): 'shallow' [proc declared in /home/runner/work/Nim/Nim/lib/system.nim(2809, 6)]�[36m�[0m�[0m
2022-07-28T11:12:09.4193277Z        Tip: 9 messages have been suppressed, use --verbose to show them.
2022-07-28T11:12:09.4193601Z      Error: Build failed for package: c2nim
2022-07-28T11:12:09.4193897Z         ... Execution failed with exit code 1
2022-07-28T11:12:09.4194754Z         ... Command: /home/runner/work/Nim/Nim/bin/nim c --colors:on --noNimblePath -d:release -d:NimblePkgVersion=0.9.18 --hints:off -o:'/tmp/nimble_20270/githubcom_nimlangc2nim_#head/c2nim' '/tmp/nimble_20270/githubcom_nimlangc2nim_#head/c2nim.nim'