Remove deprecated sigv4 module (#737)

Remove deprecated sigv4 module, this has been migrated to
https://github.com/prometheus/sigv4.

Signed-off-by: SuperQ <[email protected]>

Author: SuperQ

.circleci/config.yml

@@ -25,7 +25,6 @@ jobs:
             - go/load-cache:
                 key: v1-go<< parameters.go_version >>
       - run: make test
-      - run: make -C sigv4 test
       - when:
           condition: << parameters.use_gomod_cache >>
           steps:
@@ -74,7 +73,6 @@ jobs:
             - go/load-cache:
                 key: v1-go<< parameters.go_version >>
       - run: make style
-      - run: make -C sigv4 style
       - run: make -C assets style
       - run: make check-go-mod-version
       - when:

.github/dependabot.yml

@@ -8,7 +8,3 @@ updates:
     directory: "/assets"
     schedule:
       interval: monthly
-  - package-ecosystem: "gomod"
-    directory: "/sigv4"
-    schedule:
-      interval: monthly