fix docstring identation

Author: manoelmarques

qiskit/aqua/algorithms/eigen_solvers/numpy_eigen_solver.py

@@ -189,7 +189,7 @@ def _run(self):
         Returns:
             dict: Dictionary of results
         Raises:
-             AquaError: if no operator has been provided
+            AquaError: if no operator has been provided
         """
         if self._operator is None:
             raise AquaError("Operator was never provided")

requirements-dev.txt

@@ -4,7 +4,7 @@ ddt>=1.2.0
 pycodestyle
 pylint>=2.4.3
 pylintfileheader>=0.0.2
-Sphinx>=1.8.3,<3.0
+Sphinx>=1.8.3
 sphinx-rtd-theme>=0.4.0
 sphinx-tabs>=1.1.11
 sphinx-autodoc-typehints