.github/dependabot.yml: clear out ignored updates

These are all old, I think. If they're not, we can re-ignore them.

.github/dependabot.yml

@@ -5,31 +5,3 @@ updates:
   schedule:
     interval: weekly
   open-pull-requests-limit: 10
-  ignore:
-  - dependency-name: futures
-    versions:
-    - ">= 0.3.a, < 0.4"
-  - dependency-name: headers
-    versions:
-    - ">= 0.3.a, < 0.4"
-  - dependency-name: hyper
-    versions:
-    - "< 0.12, >= 0.11.a"
-  - dependency-name: hyper
-    versions:
-    - ">= 0.13.a, < 0.14"
-  - dependency-name: hyper
-    versions:
-    - ">= 0.14.a, < 0.15"
-  - dependency-name: reqwest
-    versions:
-    - ">= 0.10.a, < 0.11"
-  - dependency-name: tokio
-    versions:
-    - ">= 0.2.a, < 0.3"
-  - dependency-name: tokio
-    versions:
-    - ">= 0.3.a, < 0.4"
-  - dependency-name: tokio
-    versions:
-    - ">= 1.a, < 2"