[docs] Fix warnings in ConstantInterpreter

Fixed following trivial issues that caught by warnings by adding
indents.

clang/docs/ConstantInterpreter.rst:133: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:136: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:153: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:195: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:225: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:370: WARNING: Bullet list ends
without a blank line; unexpected unindent.
clang/docs/ConstantInterpreter.rst:383: WARNING: Bullet list ends
without a blank line; unexpected unindent.