Typo (Lightning-AI#2575)

* Typo

* Update docs/source/performance.rst

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

Author: tejasvi

Diff for: docs/source/performance.rst

@@ -24,7 +24,7 @@ some references, [`1 <https://discuss.pytorch.org/t/guidelines-for-assigning-num
 
 .. warning:: Increasing num_workers will ALSO increase your CPU memory consumption.
 
-The best thing to do is to increase the nun_workers slowly and stop once you see no more improvement in your training speed.
+The best thing to do is to increase the `num_workers` slowly and stop once you see no more improvement in your training speed.
 
 Spawn
 ^^^^^
@@ -94,4 +94,4 @@ However, know that 16-bit and multi-processing (any DDP) can have issues. Here a
         # will see what the error is
         CUDA_LAUNCH_BLOCKING=1 python main.py
 
-We also recommend using 16-bit native found in PyTorch 1.6. Just install this version and Lightning will automatically use it.
+We also recommend using 16-bit native found in PyTorch 1.6. Just install this version and Lightning will automatically use it.