Remove docs on multidispatch since separated back to generic library

Signed-off-by: Dan Yeaw <dan@yeaw.me>

docs/index.rst

@@ -45,7 +45,6 @@ Tech section
    undo
    xml-format
    event_system
-   multidispatching
 
 .. toctree::
    :maxdepth: 2

docs/multidispatching.md

@@ -1,94 +0,0 @@
-# Multi-Dispatching
-
-Multidispatching allows Gaphor to define methods and functions which should
-behave differently based on the argument types without cluttering
-`if-elif-else` chains and `isinstance` calls.
-
-All you need is inside `gaphor.utils.generic.multidispatch` module. See examples
-below to learn how to use it to define multifunctions and multimethods.
-
-## Multifunctions
-
-Suppose we want to define a function which behaves differently based on
-arguments' types. One solution may be to inspect argument types with
-`isinstance` function calls but generic provides us with
-`@multidispatch` decorator which can easily reduce the amount of
-boilerplate and provide desired level of extensibility:
-
-    from gaphor.utils.generic.multidispatching import multidispatch
-
-    @multidispatch(Dog)
-    def sound(o):
-      print("Woof!")
-
-    @sound.when(Cat)
-    def sound(o):
-      print("Meow!")
-
-Each separate definition of `sound` function works for different
-argument types, we will call each such definition *a multidispatch case*
-or simply *a case*. We can test if our `sound` multidispatch works as
-expected:
-
-    >>> sound(Dog())
-    Woof!
-    >>> sound(Cat())
-    Meow!
-    >>> sound(Duck())
-    Traceback
-    ...
-    TypeError
-
-The main advantage of using multifunctions over single function with a
-bunch of `isinstance` checks is extensibility \-- you can add more cases
-for other types even in separate module:
-
-    from somemodule import sound
-
-    @sound.when
-    def sound(o)
-      print("Quack!")
-
-When behaviour of multidispatch depends on some argument we will say
-that this multidispatch *dispatches* on this argument.
-
-## Multifunctions of Several Arguments
-
-You can also define multifunctions of several arguments and even decide
-on which of first arguments you want to dispatch. For example the
-following function will only dispatch on its first argument while
-requiring both of them:
-
-    @multidispatch(Dog)
-    def walk(dog, meters):
-      print(f"Dog walks for {meters} meters")
-
-But sometimes you want multifunctions to dispatch on more than one
-argument, then you just have to provide several arguments to
-`multidispatch` decorator and to subsequent `when` decorators:
-
-    @multidispatch(Dog, Cat)
-    def chases(dog, cat):
-      return True
-
-    @chases.when(Dog, Dog)
-    def chases(dog, dog):
-      return None
-
-    @chases.when(Cat, Dog)
-    def chases(cat, dog):
-      return False
-
-You can have any number of arguments to dispatch on but they should be
-all positional, keyword arguments are allowed for multifunctions only if
-they're not used for dispatch.
-
-## API reference
-
-```eval_rst
-.. autoclass:: gaphor.misc.generic.multidispatch.multidispatch
-```
-
-```eval_rst
-.. autoclass:: gaphor.misc.generic.multidispatch.FunctionDispatcher
-```