ci: Remove failpoint feature from CI runs

Also remove from developer docs

Author: sourcefrog

.github/workflows/rust.yml

@@ -55,8 +55,7 @@ jobs:
           cargo --version
           rustc --version
       - name: Test
-        run: >
-          cargo test --features fail/failpoints
+        run: cargo test
       # S3 integration tests can't run from CI because they need credentials, but we
       # can at least make sure that they compile.
       - name: cargo build --all-targets --all-features
@@ -92,13 +91,11 @@ jobs:
           cargo --version
           rustc --version
       - name: Build
-        run: cargo build --all-targets --features fail/failpoints
+        run: cargo build --all-targets
       - name: Test (without mount)
-        run: cargo test --features fail/failpoints -- --skip mount
-          --include-ignored
+        run: cargo test -- --skip mount --include-ignored
       - name: Test (mount)
-        run: cargo test --features fail/failpoints --test mount --
-          --include-ignored
+        run: cargo test --test mount -- --include-ignored
         env:
           # Running multiple instances in parallel might cause a crash on low-end environments
           # when executing the mounting tests on Windows due to projfs.
@@ -128,7 +125,6 @@ jobs:
         run: >
           cargo mutants --no-shuffle -vV --in-diff git.diff --in-place
           --no-default-features
-          --features fail/failpoints
       - name: Archive mutants.out
         uses: actions/upload-artifact@v4
         if: always()
@@ -160,7 +156,6 @@ jobs:
           cargo mutants --no-shuffle -vV --in-place --baseline=skip
           --shard ${{ matrix.shard }}/10
           --no-default-features
-          --features fail/failpoints
       - name: Archive results
         uses: actions/upload-artifact@v4
         if: always()

CONTRIBUTING.md

@@ -34,8 +34,6 @@ This is enough for normal iterative development. There are also some special tes
 
 `cargo test -- --include-ignored` runs some property-based tests that are slower (taking about a minute).
 
-`cargo test --features fail/failpoints` runs tests that use Rust [failpoints](https://docs.rs/fail/) to exercise error handling.
-
 `cargo test --features s3-integration-tests` runs tests that create real AWS S3 buckets and objects. These tests are slow and require AWS credentials to be set up. The buckets should be automatically cleaned up after the tests, but be aware that they are real resources and may incur (small) costs. I'd recommend you run this with credentials for an account that doesn't contain any important data, just in case.
 
 ## Adding new tests