fix(actions): keep folded block scalars intact across serialization (#39787)

Folded (`>`) scalars in workflows gained blank lines and had spaces
turned into newlines every time Gitea re-serialized a job. This bumps
go-yaml to its main branch and drops our workarounds. The runner gets
the same change in https://gitea.com/gitea/runner/pulls/1321.

- go-yaml main fixes the accumulating blank lines
(https://github.com/yaml/go-yaml/pull/366) and the block scalar
indentation indicators (https://github.com/yaml/go-yaml/pull/414), so
`BlockSafeString` and the folded scalar requoting go away
- The job encoder no longer wraps lines, because go-yaml still wraps
more-indented lines of folded scalars and turns a space into a newline
- The fix applies to folded scalars anywhere in a workflow, including
workflow-level `env`

Fixes https://github.com/go-gitea/gitea/issues/39775
Co-authored-by: silverwind <me@silverwind.io>

modules/actions/jobparser/testdata/prefixed_newline.out.yaml

@@ -7,5 +7,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - id: extract_tag
-        name: "\nExtract tag for variant"
-        run: "\necho Test\n"
+        name: |-
+
+          Extract tag for variant
+        run: |
+
+          echo Test