ci(nvim): lower required nvim version to v0.6 (#280)

Author: linrongbin16

.github/workflows/ci.yml

@@ -47,7 +47,7 @@ jobs:
     name: Unit Test
     strategy:
       matrix:
-        nvim_version: [stable, nightly, v0.7.0]
+        nvim_version: [stable, nightly, v0.6.0]
     runs-on: ubuntu-latest
     steps:
       - name: Checkout