Remove specs for EIP-6914 (#5568)

[EIP-6914](https://eips.ethereum.org/EIPS/eip-6914) is stagnant and is
not expected to be included in upcoming upgrades. With that in mind, I
believe we should remove these specifications. If/when this EIP is
proposed for an upgrade in the future, we can add them back.

Author: jtraglia

.github/labeler.yml

@@ -61,13 +61,6 @@ heze:
       - 'presets/*/heze.yaml'
       - 'pysetup/spec_builders/heze.py'
 
-eip6914:
-  - changed-files:
-    - any-glob-to-any-file:
-      - 'specs/_features/eip6914/**'
-      - 'presets/*/eip6914.yaml'
-      - 'pysetup/spec_builders/eip6914.py'
-
 eip8025:
   - changed-files:
     - any-glob-to-any-file:

.github/release-drafter.yml

@@ -38,9 +38,6 @@ categories:
         - eip7805
 
   # Features
-  - title: EIP-6914
-    when:
-      label: eip6914
   - title: EIP-8025
     when:
       label: eip8025