Do not use SyntaxError#path

[justinko]

Fixes #52089

From what I understand, path is only set in the context of eval. When explicitly raising SyntaxError, path is nil.

Regardless of how SyntaxError is raised, the "path" always exists in SyntaxError#to_s. Therefore, we should just use #to_s.

Here is an example of the difference between path (when it's present) and to_s (the first line is path):

"(eval at /Users/jko/Developer/rails/rails/actionpack/test/dispatch/debug_exceptions_test.rb:106)"
"(eval at /Users/jko/Developer/rails/rails/actionpack/test/dispatch/debug_exceptions_test.rb:106):1: syntax error, unexpected end-of-input\nbroke_syntax =\n              ^\n"

I see no reason to use the convenience method path and it was chosen because it's simpler.

Perhaps path not being populated outside eval is a Ruby bug?

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