Remove unused CI instructions

- Update requirementslib in `vendor.txt`

Signed-off-by: Dan Ryan <dan.ryan@canonical.com>

.buildkite/pipeline.yml

@@ -1,5 +0,0 @@
-steps:
-  - label: ":python:"
-    commands:
-      # - make
-      - ./run-tests.sh

.buildkite/project.json

@@ -1,10 +0,0 @@
-{
-  "name": "Pipenv Test Suite",
-  "steps": [
-    {
-      "type": "script",
-      "name": ":pipeline:",
-      "command": "buildkite-agent pipeline upload"
-    }
-  ]
-}

pipenv/vendor/vendor.txt

@@ -26,7 +26,7 @@ requests==2.23.0
     idna==2.9
     urllib3==1.25.9
     certifi==2020.4.5.1
-requirementslib==1.5.6
+requirementslib==1.5.7
     attrs==19.3.0
     distlib==0.3.0
     packaging==20.3