Add back pull request to linting action (#4032)

.github/workflows/linting.yml

@@ -9,6 +9,8 @@ env:
   PIP_DEFAULT_TIMEOUT: 100
 
 on:
+  pull_request:
+    types: [opened, synchronize, edited]
   push:
     branches:
       - 'feature/*'
@@ -17,7 +19,7 @@ on:
 
 # Cancel previous runs that are not yet completed.
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.event_name }}-${{ github.repository }}-${{ github.ref }}
   cancel-in-progress: true
 
 jobs:

build/conda/conda-3-9-env-full.yaml

@@ -6,4 +6,3 @@ dependencies:
   - pip
   - poetry=1.1.13
   - lightgbm=3.3.3
-  - charset-normalizer=2.1.1