ci: fix indentation in WASM

Incorrect indentation causes Github to report "syntax error on line 1" and silently
disable all of the checks in this library. For example, see
https://github.com/apoelstra/rust-secp256k1/actions/runs/17178718613/workflow

Author: apoelstra

.github/workflows/rust.yml

@@ -253,19 +253,19 @@ jobs:
       - name: "Run test on i686"
         run: cargo test --target i686-unknown-linux-gnu
 
- WASM:
-   name: WASM - stable toolchain
-   runs-on: ubuntu-latest
-   strategy:
-     fail-fast: false
-     # Note we do not use the recent lock file for wasm testing.
-   steps:
-     - name: "Checkout repo"
-       uses: actions/checkout@v4
-     - name: "Select toolchain"
-       uses: dtolnay/rust-toolchain@stable
-     - name: "Run wasm script"
-       run: ./contrib/wasm.sh
+  WASM:
+    name: WASM - stable toolchain
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      # Note we do not use the recent lock file for wasm testing.
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Select toolchain"
+        uses: dtolnay/rust-toolchain@stable
+      - name: "Run wasm script"
+        run: ./contrib/wasm.sh
 
   NoStd:                      # 1 job, run no-std test from script.
     name: no-std - nightly toolchain