Update agate requirement from ~=1.7.0 to >=1.7,<1.9 in /core

Updates the requirements on [agate](https://github.com/wireservice/agate) to permit the latest version.
- [Changelog](https://github.com/wireservice/agate/blob/master/CHANGELOG.rst)
- [Commits](wireservice/agate@1.7.0...1.8.0)

---
updated-dependencies:
- dependency-name: agate
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

core/setup.py

@@ -49,7 +49,7 @@
         # ----
         # dbt-core uses these packages deeply, throughout the codebase, and there have been breaking changes in past patch releases (even though these are major-version-one).
         # Pin to the patch or minor version, and bump in each new minor version of dbt-core.
-        "agate~=1.7.0",
+        "agate>=1.7,<1.9",
         "Jinja2~=3.1.2",
         "mashumaro[msgpack]~=3.9",
         # ----