[CircleCI] Drop Swift < 4.2

.circleci/config.yml

@@ -25,41 +25,6 @@ jobs:
       xcode: "10.0.0"
     <<: *xcode
 
-  linux_swift_4:
-    docker:
-      - image: norionomura/swift:40
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.0.2:
-    docker:
-      - image: norionomura/swift:402
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.0.3:
-    docker:
-      - image: norionomura/swift:403
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.1:
-    docker:
-      - image: norionomura/swift:41
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.1.1:
-    docker:
-      - image: norionomura/swift:411
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.1.2:
-    docker:
-      - image: norionomura/swift:412
-    steps: *steps-for-swiftpm
-
-  linux_swift_4.1.3:
-    docker:
-      - image: norionomura/swift:413
-    steps: *steps-for-swiftpm
-
   linux_swift_4.2:
     docker:
       - image: norionomura/swift:42
@@ -70,11 +35,4 @@ workflows:
   workflow:
     jobs:
       - xcode_10_swift_4.2
-      - linux_swift_4
-      - linux_swift_4.0.2
-      - linux_swift_4.0.3
-      - linux_swift_4.1
-      - linux_swift_4.1.1
-      - linux_swift_4.1.2
-      - linux_swift_4.1.3
       - linux_swift_4.2