Remove plugins chapter

we don't want to support plugins

src/doc/rustdoc/src/SUMMARY.md

@@ -4,5 +4,4 @@
 - [Command-line arguments](command-line-arguments.md)
 - [In-source directives](in-source-directives.md)
 - [Documentation tests](documentation-tests.md)
-- [Plugins](plugins.md)
-- [Passes](passes.md)
+- [Passes](passes.md)

src/doc/rustdoc/src/command-line-arguments.md

@@ -141,20 +141,6 @@ Similar to `--library-path`, `--extern` is about specifying the location
 of a dependency. `--library-path` provides directories to search in, `--extern`
 instead lets you specify exactly which dependency is located where.
 
-
-## `--plugin-path`: loading plugins
-
-Using this flag looks like this:
-
-```bash
-$ rustdoc src/lib.rs --plugin-path=/path/to/plugins
-```
-
-Similar to `--library-path`, but for plugins. For more, see
-the [chapter on plugins](plugins.html).
-
-See also: `--plugins`.
-
 ## `--passes`: add more rustdoc passes
 
 Using this flag looks like this:
@@ -171,18 +157,6 @@ For more details on passes, see [the chapter on them](passes.html).
 
 See also `--no-defaults`.
 
-## `--plugins`: 
-
-Using this flag looks like this:
-
-```bash
-$ rustdoc src/lib.rs --plugins foo bar
-```
-
-For more, see the [chapter on plugins](plugins.html).
-
-See also: `--plugin-path`.
-
 ## `--no-defaults`: don't run default passes
 
 Using this flag looks like this:
@@ -345,4 +319,4 @@ $ rustdoc src/lib.rs --sysroot /path/to/sysroot
 ```
 
 Similar to `rustc --sysroot`, this lets you change the sysroot `rustdoc` uses
-when compiling your code.
+when compiling your code.