ci: Remove licenseheaders pre-commit check

The `licenseheaders` tool has a number of issues which make it
unsuitable for our CI:

- It's not smart enough to know when it should apply a single year or a
  year range to touched files. No combination of options or templates
  can handle this.

- If a license header contains multiple contributor lines and year
  ranges, they are blindly overwritten with the license template. It's
  impossible to create a template to handle this.

- It can't be ran on all files because it will try to update all
  existing files whether they've actually been changed or not.

Author: rwalton-arm

.pre-commit-config.yaml

@@ -1,12 +1,4 @@
 repos:
-  - repo: https://github.com/kdeyev/licenseheaders.git
-    rev: 'master'
-    hooks:
-      - id: licenseheaders
-        exclude: \.yaml$|\.yml$
-        args: ["-s", "ci_scripts/licenseheaders.json", "-t",
-        "ci_scripts/templates/.copyright.tmpl", "-cy", "-f"]
-
   - repo: https://github.com/psf/black
     rev: 19.10b0
     hooks: