[main][Docs] Fix spelling errors across documentation (#6649)

Fix various spelling mistakes in the project documentation to improve
clarity and correctness.
- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd

---------

Signed-off-by: SlightwindSec <slightwindsec@gmail.com>

docs/source/user_guide/feature_guide/Multi_Token_Prediction.md

@@ -109,7 +109,7 @@ if self.speculative_config:
         got {self.decode_threshold}"
 ```
 
-## Limitation
+## Limitations
 
 - Due to the fact that only a single layer of weights is exposed in DeepSeek's MTP, the accuracy and performance are not effectively guaranteed in scenarios where MTP > 1 (especially MTP ≥ 3). Moreover, due to current operator limitations, MTP supports a maximum of 15.
 - In the fullgraph mode with MTP > 1, the capture size of each aclgraph must be an integer multiple of (num_speculative_tokens + 1).

docs/source/user_guide/feature_guide/weight_prefetch.md

@@ -29,7 +29,7 @@ However, this may not be the optimal configuration for your scenario. For higher
 Notices:
 
 1) Weight prefetch of MLP `down` project prefetch dependence sequence parallel, if you want open for mlp `down` please also enable sequence parallel.
-2) Due to the current size of the L2 cache, the maximum prefetch cannot exceed 18MB. If `prefetch_ration * lineaer_layer_weight_size >= 18 * 1024 * 1024` bytes, the backend will only prefetch 18MB.
+2) Due to the current size of the L2 cache, the maximum prefetch cannot exceed 18MB. If `prefetch_ratio * linear_layer_weight_size >= 18 * 1024 * 1024` bytes, the backend will only prefetch 18MB.
 
 ## Example