Only use swift 5.5

Author: Andrewangeta

.github/workflows/test.yaml

@@ -10,9 +10,6 @@ jobs:
       fail-fast: false
       matrix:
         swiftver:
-          - 'swift:5.2'
-          - 'swift:5.3'
-          - 'swift:5.4'
           - 'swift:5.5'
           - 'swiftlang/swift:nightly-main'
         swiftos: