CI: update perl-actions and actions/checkout

.github/workflows/ci.yml

@@ -16,9 +16,9 @@ jobs:
             experimental: true
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Install prove
-        uses: perl-actions/install-with-cpanm@v1
+        uses: perl-actions/install-with-cpanm@v1.5
         with:
           install: "Test::Nginx"
           tests: false

README.md

@@ -96,10 +96,9 @@ All colons (*:*) in the server names get replaced with underscores (*_*).
 
 ### Where this can be useful
 
-Hmm, I do not know. Anyway, a singlet upstream is a prominent category because
-it declares a single server with fallback mode. We can use them to provide
-robust HTTP session management when backend servers identify themselves using a
-known mechanism like HTTP cookies.
+A singlet upstream declares a single server with fallback mode. This can be used
+to manage sticky HTTP sessions when backend servers identify themselves using a
+proper mechanism such as HTTP cookies.
 
 ```nginx
 upstream  uhost {