restrict GitHub Actions workflow permissions (#5840)

.github/workflows/lint.yml

@@ -6,6 +6,9 @@ on:
   pull_request:
     branches: [main]
 
+permissions:
+  contents: read
+
 jobs:
   go:
     runs-on: ubuntu-24.04

.github/workflows/nightly_binaries.yml

@@ -3,6 +3,9 @@ name: nightly_binaries
 on:
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   nightly_binaries:
     runs-on: ubuntu-24.04

.github/workflows/test.yml

@@ -6,6 +6,9 @@ on:
   pull_request:
     branches: [main]
 
+permissions:
+  contents: read
+
 jobs:
   test_64:
     runs-on: ubuntu-24.04