docs: Reference requirements.psd1 instead of duplicating versions

The dependency table in the repository-specific instructions duplicated
the pinned versions from requirements.psd1 and drifted whenever they
changed. Replace the version column with each module's purpose and point
to requirements.psd1 as the source of truth. Also drop the hardcoded
module version and task-runner version numbers for the same reason.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JHgRWPi4D2aun7CEtwLz7T

Author: tablackburn

instructions/repository-specific.instructions.md

@@ -14,10 +14,10 @@ file only adds repo-specific concepts.
 **PowerShellBuild** is a PowerShell module that provides standardized build, test, and publish
 tasks for other PowerShell module projects. It supports two task-runner frameworks:
 
-- **psake** (4.9.0+)
-- **Invoke-Build** (5.8.1+)
+- **psake**
+- **Invoke-Build**
 
-- Current version: **0.8.1** (see `PowerShellBuild/PowerShellBuild.psd1`)
+- Current version: see `ModuleVersion` in `PowerShellBuild/PowerShellBuild.psd1`
 - `PowerShellVersion` in the manifest is currently `'3.0'` — almost certainly wrong; under
   review in the v1.0.0 roadmap (psake/PowerShellBuild#120)
 - Cross-platform: Windows, Linux, macOS (CI matrix in `.github/workflows/test.yml`)
@@ -220,16 +220,17 @@ no-ops on non-Windows.
 
 ## Dependencies
 
-Defined in `requirements.psd1`, installed via **PSDepend** when `./build.ps1 -Bootstrap` runs:
-
-| Module           | Version  |
-| ---------------- | -------- |
-| BuildHelpers     | 2.0.16   |
-| Pester           | 5.8.0    |
-| psake            | 4.9.0    |
-| PSScriptAnalyzer | 1.25.0   |
-| InvokeBuild      | 5.8.1    |
-| platyPS          | 0.14.2   |
+Defined in `requirements.psd1` — the source of truth for build-dependency names and pinned
+versions — and installed via **PSDepend** when `./build.ps1 -Bootstrap` runs:
+
+| Module           | Purpose                                                    |
+| ---------------- | ---------------------------------------------------------- |
+| BuildHelpers     | Populates the `BH*` build environment variables            |
+| Pester           | Test framework                                             |
+| psake            | Task runner for this repo's own build                      |
+| PSScriptAnalyzer | Static analysis of the built module                        |
+| InvokeBuild      | Alternate task runner (consumer-facing `IB.tasks.ps1`)     |
+| platyPS          | Help and documentation generation                          |
 
 ## Testing