Fix vec import in common migrations

[Agusrodri]

What does it do?

Fix a compilation error while building the tracing runtimes:

Build moonbase-2800-substitute-tracing…
║ 🧰 Substrate Runtime Toolbox - srtool v0.13.0 🧰
║ - by Chevdor -
info: using existing install for '1.74.0-x86_64-unknown-linux-gnu'
info: override toolchain for '/build' set to '1.74.0-x86_64-unknown-linux-gnu'
║
║ 1.74.0-x86_64-unknown-linux-gnu unchanged - rustc 1.74.0 (79e9716c9 2023-11-13)
...
║ error: cannot find macro `vec` in this scope
║ --> /home/builder/cargo/git/checkouts/moonbeam-43ea08ca2e3f6df3/e2fae82/runtime/common/src/migrations.rs:326:3
║ |
║ 326 | vec![
║ | ^^^
║ |
║ help: consider importing one of these items
║ |
║ 26 + use frame_benchmarking::__private::vec;
║ |
║ 26 + use parity_scale_codec::alloc::vec;
║ |
║ 26 + use sp_api::vec;
║ |
║ 26 + use sp_std::vec;
║ |
║
║ error: could not compile `moonbeam-runtime-common` (lib) due to previous error

The error exists only for moonbase.

[noandrea]

🦸

[github-actions]

Coverage Report

@@                  Coverage Diff                  @@
##           master   agustin-fix-import     +/-   ##
=====================================================
  Coverage   73.68%               73.68%   0.00%     
  Files         232                  232             
+ Lines       72749                72750      +1     
=====================================================
- Hits        53604                53603      -1     
+ Misses      19145                19147      +2     

Files Changed	Coverage

Coverage generated Thu Feb 22 21:53:40 UTC 2024