Missing await in async similarity_search example

### Submission checklist - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [ ] langchain - [ ] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [x] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs _No response_ ### Reproduction Steps / Example Code (Python) ```python from langchain_qdrant import QdrantVectorStore # async call without await results = vector_store.asimilarity_search(query="thud", k=1) print(results) ``` ### Error Message and Stack Trace (if applicable) ```shell ``` ### Description The async example in the QdrantVectorStore docstring is missing an `await` for `asimilarity_search`. Current example: `results = vector_store.asimilarity_search(query="thud", k=1)` This returns a coroutine instead of actual results when executed. Expected behavior: `results = await vector_store.asimilarity_search(query="thud", k=1)` This is also inconsistent with the other async examples in the same section, which correctly use `await`. Suggested fix: Add `await` to the `asimilarity_search` call in the async example. ### Syst…