[text-auditor] Fix clear grammar issues in runtime errors and docs

## Text Improvements

The following user-facing text issues were found in the repository. Each is a low-effort fix. Existing `/tmp/previous-findings.json`, current open `[text-auditor]` issues, and recent PRs were checked; candidates already tracked by issues such as #51325 and #51419 were excluded.

### 1. `requires to` grammar in user-facing runtime/docs text

**Files:**
- `filebeat/beater/filebeat.go` (line 172)
- `docs/reference/filebeat/file-identity.md` (line 58)
- `docs/extend/index.md` (line 103)
- `testing/environments/README.md` (line 61)

**Current text:**
- `stdin requires to be run in exclusive mode, configured inputs: %s`
- `The most unstable option, requires to maintain immutable file paths.`
- `On Debian/Ubuntu systems it also requires to install the `python3-venv` package, that includes additional support scripts:`
- `This requires to shut down an environment and clean it up before starting another environment.`

**Suggested fix:**
- `stdin must be run in exclusive mode, configured inputs: %s`
- `The most unstable option; requires maintaining immutable file paths.`
- `On Debian/Ubuntu systems, you also need to install the `python3-venv` package, which includes additional support scripts:`
- `This requires shutting down an environment and cleaning it up before starting another environment.`

**Why:** `requires to` is ungrammatical in these user-facing error and documentation sentences.

### 2. Azure runtime error says `configurations options`

**File:** `x-pack/metricbeat/module/azure/azure.go` (line 246)

**Current text:** `no resources were found based on all the configurations options entered`

**Suggested fix:** `no resources were found based on all the configuration options entered`

**Why:** `configurations options` is a clear noun/adjective grammar error in a returned runtime error. The same phrase also appears in Azure debug log strings and a test expectation, so an exact-string search can update the family consistently.

### 3. Azure missing-metric-definitions message ends with incomplete wording

**File:** `x-pack/metricbeat/module/azure/monitor/client_helper.go` (line 21)

**Current text:** `no metric definitions were found for resource %s and namespace %s. Verify if the namespace is spelled correctly or if it is supported by the resource in case`

**Suggested fix:** `no metric definitions were found for resource %s and namespace %s. Verify that the namespace is spelled correctly and that the resource supports it`

**Why:** The trailing `in case` leaves the user-facing info/error message grammatically incomplete. This constant is emitted through `client.Log.Infof` and returned as an error in `x-pack/metricbeat/module/azure/monitor/client_helper.go` (lines 48 and 52), with the same constant used by the concurrent helper at `x-pack/metricbeat/module/azure/monitor/client_helper_concurrent.go` (lines 58 and 61).

## Suggested Actions

- [ ] Replace the verified `requires to` instances above with grammatical wording and update the matching Filebeat stdin test expectation.
- [ ] Replace `configurations options` with `configuration options` in the Azure runtime error family.
- [ ] Remove the incomplete trailing `in case` from the Azure missing-metric-definitions message.

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[What is this?](https://ela.st/github-ai-tools) | [From workflow: Text Auditor](https://github.com/elastic/beats/actions/runs/28174689192)

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> - [x] expires on Jul 2, 2026, 2:56 PM UTC

Start with the four listed Filebeat and documentation files, then inspect x-pack/metricbeat/module/azure/azure.go and the Azure monitor helper files. Search for the exact Azure strings to find matching debug logs and test expectations, and run the relevant Filebeat stdin test. Done means all listed user-facing wording is corrected consistently and the affected tests pass.

Written by the indexing model from the issue text.