Added flask-wtf<1.1.0 to requirements.pip.

(Redmine issue: #7622)

conf/requirements.pip

@@ -17,7 +17,7 @@ flask-mail>=0.9.1,<1.0.0
 flask-migrate>=3.1.0,<4.0.0
 flask-babel>=2.0.0,<3.0.0
 flask-principal>=0.4.0,<1.0.0
-flask-wtf>=1.0.1,<2.0.0
+flask-wtf>=1.0.1,<1.1.0
 flask-script>=2.0.6,<3.0.0
 flask-sqlalchemy>=2.5.1,<3.0.0
 flask-debugtoolbar>=0.13.1,<1.0.0