chore: cleanup instructions in MIGRATION file (#11975)

Author: sjrl

MIGRATION.md

@@ -4,75 +4,8 @@ This document is meant to provide a guide for migrating from Haystack v2.X to v3
 
 ---
 
-## How to Document a Breaking Change
-
-When you merge a breaking change into the v3 branch, add an entry to this file under the appropriate section below.
-Follow this structure:
-
-### Entry template
-
-```markdown
-### <Short title describing what changed>
-
-**What changed:** One or two sentences describing the change — what was removed, renamed, or altered.
-
-**Why:** Brief motivation (e.g. simplification, API consistency, dependency reduction).
-
-**How to migrate:**
-
-Before (v2.x):
-\`\`\`python
-# example using the old API
-from haystack.components.foo import OldComponent
-component = OldComponent(old_param="value")
-\`\`\`
-
-After (v3.0):
-\`\`\`python
-# example using the new API
-from haystack.components.foo import NewComponent
-component = NewComponent(new_param="value")
-\`\`\`
-```
-
-### Tips
-
-- **One entry per breaking change.** Don't bundle unrelated changes into a single entry.
-- **Include a working code example** for every rename, removal, or signature change.
-- **Link to the PR** when extra context would help (e.g. `See [#1234](https://github.com/deepset-ai/haystack/pull/1234)`).
-- **Components moved to external packages** don't need a full entry: add a row to the table in
-  [Components Moved to External Packages](#components-moved-to-external-packages) instead.
-
----
-
 ## Breaking Changes
 
-<!-- Add entries here as v3 development progresses. Example below shows the expected format. -->
-
-### Example entry: `Document.dataframe` field removed
-
-**What changed:** The `dataframe` field on `Document` and the `ExtractedTableAnswer` dataclass have been removed. `pandas` is no longer a required dependency.
-
-**Why:** Reduces the default installation footprint. Components that need `pandas` will raise an informative error prompting the user to install it explicitly.
-
-**How to migrate:**
-
-Before (v2.x):
-```python
-from haystack.dataclasses import Document
-import pandas as pd
-
-doc = Document(content=pd.DataFrame({"col": [1, 2, 3]}))
-```
-
-After (v3.0):
-```python
-# Store tabular data as plain content or create a custom component that returns pandas DataFrames as needed.
-from haystack.dataclasses import Document
-
-doc = Document(content="col\n1\n2\n3")
-```
-
 ### `GeneratedAnswer` and `ExtractedAnswer` serialization format
 
 **What changed:** `GeneratedAnswer.to_dict()` and `ExtractedAnswer.to_dict()` now return a flat dictionary of the object's fields instead of wrapping them in a `{"type": ..., "init_parameters": {...}}` envelope. `from_dict()` still accepts the old wrapped format, so existing serialized artifacts keep loading.