Update requirements.txt to reflect changes to setup.cfg (#111)

These changes to the setup.cfg in colcon-core didn't get copied to this
requirements file for bootstrapping colcon.

Author: cottsay

developer/bootstrap.rst

@@ -31,7 +31,7 @@ You might want to make sure that the venv is using up-to-date versions of the so
 
 .. code-block:: bash
 
-    $ pip install -U pip setuptools
+    $ pip install -U pip 'setuptools>=40.5.0,<80'
 
 Fetch the sources
 -----------------

requirements.txt

@@ -3,6 +3,7 @@ catkin_pkg
 coloredlogs; sys_platform == 'win32'
 distlib
 EmPy
+importlib-metadata; python_version < "3.8"
 notify2; sys_platform == 'linux'
 pypiwin32; sys_platform == 'win32'
 pytest
@@ -11,4 +12,5 @@ pytest-repeat
 pytest-rerunfailures
 pytest-runner
 PyYAML
-setuptools>=40.5.0
+setuptools>=40.5.0,<80
+tomli>=1.0.0; python_version < "3.11"