Unshallow ion-c submodule

[NovemberZulu]

Description of changes:

Unshallow ion-c submodule to fix git describe failure during release workflow, example failure

Local test:

❯ git tag
❯ git describe --long --tags --dirty --match "v*"
fatal: No names found, cannot describe anything.
❯ git remote
origin
❯ git fetch --tags --unshallow
remote: Enumerating objects: 2122, done.
remote: Counting objects: 100% (2122/2122), done.
remote: Compressing objects: 100% (556/556), done.
remote: Total 1965 (delta 1548), reused 1729 (delta 1380), pack-reused 0 (from 0)
Receiving objects: 100% (1965/1965), 627.19 KiB | 4.29 MiB/s, done.
Resolving deltas: 100% (1548/1548), completed with 132 local objects.
From https://github.com/amazon-ion/ion-c
 * [new tag]         v1.0.0     -> v1.0.0
 * [new tag]         v1.0.1     -> v1.0.1
 * [new tag]         v1.0.2     -> v1.0.2
 * [new tag]         v1.0.3     -> v1.0.3
 * [new tag]         v1.0.4     -> v1.0.4
 * [new tag]         v1.0.5     -> v1.0.5
 * [new tag]         v1.0.6     -> v1.0.6
 * [new tag]         v1.1.0     -> v1.1.0
 * [new tag]         v1.1.1     -> v1.1.1
 * [new tag]         v1.1.2     -> v1.1.2
 * [new tag]         v1.1.3     -> v1.1.3
 * [new tag]         v1.1.4     -> v1.1.4
 * [new tag]         v1.4.0     -> v1.4.0
❯ git describe --long --tags --dirty --match "v*"
v1.1.4-3-g3132373

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.