fix links to prompt templates and example selectors (#6332)

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Fixes # 
links to prompt templates and example selectors on the
[Prompts](https://python.langchain.com/docs/modules/model_io/prompts/)
page are invalid.

#### Before submitting
Just a small note that I tried to run `make docs_clean` and other
related commands before PR written
[here](https://github.com/hwchase17/langchain/blob/master/.github/CONTRIBUTING.md#build-documentation-locally),
it gives me an error:
```bash
langchain % make docs_clean
Traceback (most recent call last):
  File "/Users/masafumi/Downloads/langchain/.venv/bin/make", line 5, in <module>
    from scripts.proto import main
ModuleNotFoundError: No module named 'scripts'
make: *** [docs_clean] Error 1
# Poetry (version 1.5.1)
# Python 3.9.13
```
I couldn't figure out how to fix this, so I didn't run those command.
But links should work.

#### Who can review?

Tag maintainers/contributors who might be interested:
@hwchase17

Similar issue #6323

Co-authored-by: masafumimori <m.masafumimori@outlook.com>

docs/docs_skeleton/docs/modules/model_io/prompts/index.mdx

@@ -8,5 +8,5 @@ A **prompt** refers to the input to the model.
 This input is often constructed from multiple components.
 LangChain provides several classes and functions to make constructing and working with prompts easy.
 
-- [Prompt templates](/docs/modules/prompts/prompt_templates/): Parametrize model inputs
-- [Example selectors](/docs/modules/prompts/example_selectors/): Dynamically select examples to include in prompts
+- [Prompt templates](/docs/modules/model_io/prompts/prompt_templates/): Parametrize model inputs
+- [Example selectors](/docs/modules/model_io/prompts/example_selectors/): Dynamically select examples to include in prompts