swift234

[gardening] Use consistent naming of .rst files in docs/ ("CamelCase.rst")

Fix some cases where "Camel Case.rst" is used instead of "CamelCase.rst".

File counts:
* Files in repo: 10 242
* Files in repo with spaces in file name: 10
* Files in repo with .rst suffix: 74
* Files in repo with .rst suffix and spaces in file name: 10

In addition to the consistency argument: spaces in file names create unnecessary
gotchas when it comes to bash scripting - see below.

Before this commit:

```
$ find . -name "*.rst" | xargs ls -dl > /dev/null
ls: cannot access ./docs/Dependency: No such file or directory
ls: cannot access Analysis.rst: No such file or directory
ls: cannot access ./docs/proposals/ObjC: No such file or directory
ls: cannot access Interoperation.rst: No such file or directory
ls: cannot access ./docs/proposals/C: No such file or directory
ls: cannot access Pointer: No such file or directory
ls: cannot access Argument: No such file or directory
ls: cannot access Interop.rst: No such file or directory
ls: cannot access ./docs/proposals/archive/Memory: No such file or directory
ls: cannot access and: No such file or directory
ls: cannot access Concurrency: No such file or directory
ls: cannot access Model.rst: No such file or directory
ls: cannot access ./docs/proposals/C: No such file or directory
ls: cannot access Pointer: No such file or directory
ls: cannot access Interop: No such file or directory
ls: cannot access Language: No such file or directory
ls: cannot access Model.rst: No such file or directory
ls: cannot access ./docs/proposals/rejected/Bridging: No such file or directory
ls: cannot access Container: No such file or directory
ls: cannot access Protocols: No such file or directory
ls: cannot access to: No such file or directory
ls: cannot access Class: No such file or directory
ls: cannot access Clusters.rst: No such file or directory
ls: cannot access ./docs/archive/Namespace: No such file or directory
ls: cannot access Level: No such file or directory
ls: cannot access Vars: No such file or directory
ls: cannot access and: No such file or directory
ls: cannot access Top: No such file or directory
ls: cannot access Level: No such file or directory
ls: cannot access Code.rst: No such file or directory
ls: cannot access ./docs/archive/Objective-C: No such file or directory
ls: cannot access Interoperability.rst: No such file or directory
ls: cannot access ./docs/Pattern: No such file or directory
ls: cannot access Matching.rst: No such file or directory
ls: cannot access ./docs/Failable: No such file or directory
ls: cannot access Initializers.rst: No such file or directory
$
```

After this commit:

```
$ find . -name "*.rst" | xargs ls -dl > /dev/null
$
```