Revert "'an sdist' -> 'a sdist'"

This reverts commit c29bf16.

Author: deronnax

docs/basic-usage.md

@@ -100,7 +100,7 @@ poetry init
 ### Operating modes
 
 Poetry can be operated in two different modes. The default mode is the **package mode**, which is the right mode
-if you want to package your project into a sdist or a wheel and perhaps publish it to a package index.
+if you want to package your project into an sdist or a wheel and perhaps publish it to a package index.
 In this mode, some metadata such as `name` and `version`, which are required for packaging, are mandatory.
 Further, the project itself will be installed in editable mode when running `poetry install`.
 

docs/dependency-specification.md

@@ -60,7 +60,7 @@ When both are specified, `project.dependencies` are used for metadata when build
 
 Alternatively, you can add `dependencies` to `dynamic` and define your dependencies
 completely in the `tool.poetry` section. Using only the `tool.poetry` section might
-make sense in non-package mode when you will not build a sdist or a wheel.
+make sense in non-package mode when you will not build an sdist or a wheel.
 
 ```toml
 [project]

docs/pyproject.md

@@ -307,7 +307,7 @@ dependencies = [
 ]
 ```
 
-These are the dependencies that will be declared when building a sdist or a wheel.
+These are the dependencies that will be declared when building an sdist or a wheel.
 
 See [Dependency specification]({{< relref "dependency-specification" >}}) for more information
 about the relation between `project.dependencies` and `tool.poetry.dependencies`.