Update CI and docs

Author: jackkoenig

.github/workflows/ci-circt-nightly.yml

@@ -49,7 +49,7 @@ jobs:
       matrix:
         system: ["ubuntu-24.04"]
         jvm: [21]
-        scala: ["2.13.18"]
+        scala: ["2.13"]
         espresso: ["2.4"]
         slang: ["7.0"]
         circt: ["nightly"]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         system: ["ubuntu-24.04"]
         jvm: [21]
-        scala: ["2.13.18"]
+        scala: ["2.13"]
         espresso: ["2.4"]
         slang: ["7.0"]
     uses: ./.github/workflows/test.yml

.github/workflows/test.yml

@@ -15,7 +15,7 @@ on:
         type: number
       scala:
         description: 'The Scala version to use'
-        default: '2.13.18'
+        default: '2.13'
         required: true
         type: string
       espresso:
@@ -219,7 +219,7 @@ jobs:
     runs-on: ubuntu-24.04
     strategy:
       matrix:
-        scala: ["2.13.18"]
+        scala: ["2.13"]
     steps:
       - name: Checkout
         uses: actions/checkout@v5

CONTRIBUTING.md

@@ -74,7 +74,7 @@ Most testing can be done on just the Chisel build unit:
 ```
 
 The `[]` exists because we are cross-compiling between Scala 2.13 and Scala 3.
-You can pick a specific version, e.g. `./mill chisel[2.13.18]`.
+You can pick a specific version, e.g. `./mill chisel[2.13]`.
 Using `[]` will pick the first version in the list of supported versions which one can think about as the "default" version.
 
 You can test everything with: