Fix extra semicolon in XprHelper

Reference issue

N/A

What does this implement/fix?

Fixes an extra semicolon in XprHelper, which causes compilation errors when compiled using -Wextra-semi compiler flag.

In file included from ../../third_party/eigen/Eigen/Dense:1:
In file included from ../../third_party/eigen/Eigen/Core:173:
../../third_party/eigen/Eigen/src/Core/util/XprHelper.h:828:81: error: extra ';' after member function definition [-Werror,-Wextra-semi]
  static constexpr bool is_inner_panel(bool inner_panel) { return inner_panel; };
                                                                                ^
1 error generated

Additional information