go.mod: update go-getter to the latest to avoid reported CVEs

[muvaf]

Description of your changes

v1 of terraform-plugin-sdk has reached EOL so we have to bump the dependency separately. Removal of v1 SDK completely is discussed here but this PR should unblock folks.

Fixes https://github.com/crossplane/terrajet/issues/294

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [x] Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

make reviewable