Typo fix Update adr-002-ipld-da-sampling.md (#1535)

## Description

Fix Typographical Errors in Function Descriptions

This pull request addresses and fixes critical typographical errors in
the descriptions of several functions that affect code clarity and
correctness.

#### Fixed Issues:

1. **Typo in "contex.Context"**:
- In the descriptions of the following functions:
`ValidateAvailability`, `RetrieveBlockData`, and `PutBlock`, the
reference to **"contex.Context"** has been corrected to
**"context.Context"**.
- **Importance**: This correction is crucial as the incorrect spelling
could lead to confusion or misinterpretation of the intended type,
especially for developers referencing or using these functions. Proper
naming ensures clarity, adherence to Go standards, and minimizes
potential errors or misunderstandings in documentation and code
navigation.

#### PR checklist

- [x] Tests written/updated
- [ ] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [x] Updated relevant documentation (`docs/` or `spec/`) and code
comments

---

**Please review and consider merging this fix. Thank you!**

Author: santamasa

docs/celestia-architecture/adr-002-ipld-da-sampling.md

@@ -143,7 +143,7 @@ It does not deal with IPFS internals.
 // The context can be used to provide a timeout.
 // TODO: Should there be a constant = lower bound for #samples
 func ValidateAvailability(
-    ctx contex.Context,
+    ctx context.Context,
     dah *DataAvailabilityHeader,
     numSamples int,
     onLeafValidity func(namespace.PrefixedData8),
@@ -154,7 +154,7 @@ func ValidateAvailability(
 // The key difference is that it will sample enough chunks until it can recover the
 // full extended data square, including original data (e.g. by using rsmt2d.RepairExtendedDataSquare).
 func RetrieveBlockData(
-    ctx contex.Context,
+    ctx context.Context,
     dah *DataAvailabilityHeader,
     api coreiface.CoreAPI,
     codec rsmt2d.Codec,
@@ -166,7 +166,7 @@ func RetrieveBlockData(
 // the row to the Merkle Dag, in our case a Namespaced Merkle Tree.
 // Note, that this method could also fill the DA header.
 // The data will be pinned by default.
-func (b *Block) PutBlock(ctx contex.Context, nodeAdder ipld.NodeAdder) error
+func (b *Block) PutBlock(ctx context.Context, nodeAdder ipld.NodeAdder) error
 ```
 
 We now describe the lower-level library that will be used by above methods.