[text-auditor] Fix clear grammar issues in NATS and PANW exported field descriptions

## Text Improvements

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

### 1. Fix grammar in NATS exported field description

**File:** `filebeat/module/nats/log/_meta/fields.yml` (line 49)
**Current text:** `Details about the error occurred`
**Suggested fix:** `Details about the error that occurred`
**Why:** Clear grammar error (missing connector), shown to users through exported fields docs.

### 2. Fix determiner typo in PANW exported field description

**File:** `x-pack/filebeat/module/panw/panos/_meta/fields.yml` (line 180)
**Current text:** `A string showing that error that has occurred in any event.`
**Suggested fix:** `A string showing the error that has occurred in any event.`
**Why:** Clear wording error (`that error` instead of `the error`) in user-facing field text.

### 3. Split concatenated PANW field descriptions

**File:** `x-pack/filebeat/module/panw/panos/_meta/fields.yml` (line 190)
**Current text:** `The number of sessions ... within the last five seconds.An integer associated with any errors that occurred.`
**Suggested fix:** `The number of sessions ... within the last five seconds.`
**Why:** Two descriptions are concatenated into one sentence, creating confusing exported documentation text.

### 4. Fix duplicated article in PANW exported field description

**File:** `x-pack/filebeat/module/panw/panos/_meta/fields.yml` (line 298)
**Current text:** `A string showing the how the GlobalProtect app connects to Gateway`
**Suggested fix:** `A string showing how the GlobalProtect app connects to the gateway`
**Why:** Clear grammar issue (`the how`) in user-facing field description.

## Suggested Actions

- [ ] Update the four source descriptions in `_meta/fields.yml` files listed above.
- [ ] Regenerate exported fields documentation so generated references match the corrected source text.

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> - [x] expires on Sep 16, 2026, 1:23 PM UTC

Start with the four descriptions in filebeat/module/nats/log/_meta/fields.yml and x-pack/filebeat/module/panw/panos/_meta/fields.yml at the listed lines. Correct the grammar and split the concatenated PANW text as specified, then regenerate the exported fields documentation. Done means all four source descriptions and their generated references match the requested wording.

Written by the indexing model from the issue text.