Revert "chore: configure CI for 1.x branch (#1528)"

This reverts commit 54e63ea.

Author: shobsi

.github/workflows/docs.yml

@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - v1
+      - main
 name: docs
 jobs:
   docs:

.github/workflows/lint.yml

@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - v1
+      - main
 name: lint
 jobs:
   lint:

.github/workflows/mypy.yml

@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - v1
+      - main
 name: mypy
 jobs:
   mypy:

.github/workflows/unittest.yml

@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - v1
+      - main
 name: unittest
 jobs:
   unit: