Make the file names consistent with the other workflows

Author: canova

.github/fluent/linter_config.yml .github/fluent/linter-config.yml.github/fluent/linter_config.yml renamed to .github/fluent/linter-config.yml

@@ -3,7 +3,7 @@ on:
   push:
     paths:
       - 'locales/en-US/*.ftl'
-      - '.github/workflows/fluent_linter.yml'
+      - '.github/workflows/fluent-linter.yml'
       - '.github/fluent/*'
     branches:
       - main
@@ -32,4 +32,4 @@ jobs:
           pip install -r .github/fluent/requirements.txt
       - name: Lint reference
         run: |
-          moz-fluent-lint ./locales/en-US --config .github/fluent/linter_config.yml
+          moz-fluent-lint ./locales/en-US --config .github/fluent/linter-config.yml