Fix multiple typos in murano-specs

Fix typo in specifications:
- pluggable-package-types.rst
- simulated-execution-mode-murano-engine.rst
- artifact-repository-support.rst

Change-Id: I28cd8521b9a65a213a9970d907e800528b2b7ddd

specs/liberty/artifact-repository-support.rst

@@ -118,7 +118,7 @@ Alternatives
 We may continue using murano-api to manage our packages, at least till the
 Glance v3 is STABLE, however this will require us to introduce lots of
 temporary code to support things like versioning and dependencies. So, it is
-better to add thr Glance support as an experimental feature, facade it under
+better to add the Glance support as an experimental feature, facade it under
 the python-muranoclient bindings, and migrate to it completely in the next
 release cycle.
 

specs/liberty/simulated-execution-mode-murano-engine.rst

@@ -30,7 +30,7 @@ change.
 * Those tests will be put to the application package to allow anyone to test
   this app at any time
 
-* Tests will look like regular unit tests. Testing framework, witch will
+* Tests will look like regular unit tests. Testing framework, which will
   run unit-tests will support commands, that will allow to load test package
   from directory, to call class methods and configure deployments parameters.
   That will make deployment test run easier. Also, test writer may run
@@ -279,4 +279,4 @@ New testing framework will be documented from scratch.
 References
 ==========
 
-Discussions in IRC will be provided
+Discussions in IRC will be provided

specs/mitaka/pluggable-package-types.rst

@@ -98,7 +98,7 @@ Deployer impact
 Plugins need to be deployed to each Murano node (or to all machines running
 either Murano API or Murano Engine) in order to support particular package
 type. Installation is done as usually in python (`pip install PATH` or
-`python setyp.py install` etc.)
+`python setup.py install` etc.)
 
 
 Developer impact