[text-auditor] Batch fix untracked typos in Buildkite output and Apache Spark text

## Text Improvements

The following user-facing text issues were found in the repository. Each is a low-effort fix.

### 1. `Serverles` → `Serverless` in Buildkite output

**File:** `.buildkite/scripts/test_integrations_with_serverless.sh` (line 25)
**Current text:** `Running packages on Serverles project type: \$\{SERVERLESS_PROJECT}`
**Suggested fix:** `Running packages on Serverless project type: \$\{SERVERLESS_PROJECT}`
**Why:** Clear typo in CI user-facing output.

### 2. `procesing` → `processing` in benchmark script output

**File:** `.buildkite/scripts/process_benchmarks.sh` (line 11)
**Current text:** `[benchmarks] Not a pull request build. Skip procesing benchmarks.`
**Suggested fix:** `[benchmarks] Not a pull request build. Skip processing benchmarks.`
**Why:** Clear typo in CI user-facing output.

### 3. `parallely` wording in Apache Spark metric descriptions (4 occurrences)

**File:** `packages/apache_spark/data_stream/executor/fields/fields.yml` (line 194)
**Current text:** `description: Number of jobs running parallely.`
**Suggested fix:** `description: Number of jobs running in parallel.`
**Why:** Awkward/nonstandard wording in user-facing field description.

**File:** `packages/apache_spark/data_stream/driver/fields/fields.yml` (line 334)
**Current text:** `description: Number of jobs running parallely.`
**Suggested fix:** `description: Number of jobs running in parallel.`
**Why:** Same wording issue in corresponding field description.

**File:** `packages/apache_spark/docs/README.md` (line 346)
**Current text:** `Number of jobs running parallely.`
**Suggested fix:** `Number of jobs running in parallel.`
**Why:** Same wording issue in generated package docs.

**File:** `packages/apache_spark/docs/README.md` (line 521)
**Current text:** `Number of jobs running parallely.`
**Suggested fix:** `Number of jobs running in parallel.`
**Why:** Same wording issue in generated package docs.

## Suggested Actions

- [x] Replace `Serverles` with `Serverless` in `.buildkite/scripts/test_integrations_with_serverless.sh`.
- [x] Replace `procesing` with `processing` in `.buildkite/scripts/process_benchmarks.sh`.
- [ ] Replace `running parallely` with `running in parallel` in the two Apache Spark field files and matching docs entries.

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