fix(ci): remove overly broad workflow permissions

Author: notmandatory

.github/workflows/code_coverage.yml

@@ -2,6 +2,8 @@ on: [push, pull_request]
 
 name: Code Coverage
 
+permissions: {}
+
 jobs:
   Codecov:
     name: Code Coverage

.github/workflows/cont_integration.yml

@@ -2,6 +2,8 @@ on: [push, pull_request]
 
 name: CI
 
+permissions: {}
+
 jobs:
 
   prepare:

.github/workflows/cron-update-rust.yml

@@ -1,4 +1,7 @@
 name: Update rust version
+
+permissions: {}
+
 on:
   schedule:
     - cron: "0 0 15 * *" # At 00:00 on day-of-month 15.

.github/workflows/nightly_docs.yml

@@ -1,5 +1,7 @@
 name: Publish Nightly Docs
 
+permissions: {}
+
 on: [push, pull_request]
 
 jobs: