Remove dependabot

dependabot typically isn't too useful and primarily adds noise for us.

.github/dependabot.yml

@@ -1,37 +0,0 @@
-version: 2
-updates:
-- package-ecosystem: cargo
-  directory: "/"
-  schedule:
-    interval: daily
-  open-pull-requests-limit: 10
-  assignees:
-  - Mark-Simulacrum
-  versioning-strategy: lockfile-only
-  allow:
-  - dependency-type: direct
-  - dependency-type: indirect
-  ignore:
-  - dependency-name: futures-sink
-    versions:
-    - 0.3.13
-    - 0.3.14
-  - dependency-name: futures-core
-    versions:
-    - 0.3.14
-  - dependency-name: proc-macro2
-    versions:
-    - 1.0.26
-  - dependency-name: wasm-bindgen
-    versions:
-    - 0.2.71
-    - 0.2.72
-  - dependency-name: security-framework-sys
-    versions:
-    - 2.1.1
-  - dependency-name: futures-task
-    versions:
-    - 0.3.13
-  - dependency-name: libc
-    versions:
-    - 0.2.83