Remove Julia constants that are not exported by default

[knuesel]

This PR removed a few unexported constants for Julia. These constants are defined in the Base.MathConstants module, but they are unexported. So it should not be assumed that these names (without a module prefix) represent constants in Julia code.

To illustrate, I ended up here because I was wondering why the e looks funny on https://docs.julialang.org/en/v1/base/arrays/#Base.hvcat . It turns out PrismJS treats e as a Julia constant. This is wrong: by default, someone typing e in Julia will get the error e not defined).

[RunDevelopment]

Thank for the pull request @knuesel!

The change seems reasonable. I guess you left pi and im because nobody uses them as variables?

The make the build pass, you also have to run npm run build and change Julia's constant test. More information on tests can be found here.

[knuesel]

@RunDevelopment sorry for missing that, should be fixed now.

I left im, pi, π and ℯ (which is different from e) because these ones are exported, so they are constants in a default setup.