Set version number to 0.7.5 for the release (#956)

We are about to release 0.7.5. This updates the version number in
`release/setup.py` and `tensorflow_quantum/__init__.py` to 0.7.5.

Author: mhucka

release/setup.py

@@ -31,7 +31,7 @@
 from setuptools.command.install import install
 from setuptools.dist import Distribution
 
-CUR_VERSION = "0.7.4"
+CUR_VERSION = "0.7.5"
 
 DOCLINES = __doc__.split("\n")
 

tensorflow_quantum/__init__.py

@@ -64,4 +64,4 @@
 del core
 # pylint: enable=undefined-variable
 
-__version__ = '0.7.4'
+__version__ = '0.7.5'