fix(build): revert invalid matrix syntax

Back out "test: verify matrix with stable and nightly"

This backs out commit 5fc345c0de.

.forgejo/workflows/test.yml

@@ -5,26 +5,20 @@ on:
 jobs:
   test:
     runs-on: docker
-    strategy:
-      matrix:
-        toolchain:
-          - stable
-          - nightly
-
     steps:
       - uses: actions/checkout@v4
 
-      - name: Test ${{ toolchain}}
+      - name: Test
         uses: https://git.kemitix.net/kemitix/rust@next
         with:
-          args: ${{toolchain}} cargo test
+          args: cargo test
 
-      - name: Build ${{ toolchain }}
+      - name: Build
         uses: https://git.kemitix.net/kemitix/rust@next
         with:
-          args: ${{ toolchain }} cargo build
+          args: cargo build
 
-      - name: Run ${{ toolchain }}
+      - name: Run
         uses: https://git.kemitix.net/kemitix/rust@next
         with:
-          args: ${{ toolchain }} cargo run
+          args: cargo run