Fixed some bugs in laserquantum_laser hardware file

Description

When loading the laser toolchain with the laserquantum laser it will fail upon activation. I fixed a typo when querying the shutter state get_shutter_state .
I removed the PSUTypes.FPU in get_extra_info as it is not present in PSUTypes and I could not find a matching power supply on laserquantums website
Fixed the return value of get_power_setpoint. Upon setting the power a variable _last_set_power will be set that stores the last setpoint. When querying the power setpoint this will be returned instead of the current power, which made the setpoint spinbox in the gui unusable. Upon module activation the currently set power will be retrieved. This will be close to 0 W if the laser is off or it will be the currently set output power.

First two changes prohibit the use of the laser toolchain with the laserquantum_laser hardware file
The command that was previously sent to the hardware within the if statement that I removed is not documented in the manuals for the different PSU types and returns an Error if sent to the device. Thus I removed it as no information can be gained by this query.
Setting the currently displayed setpoint to the current output power will result in an unusable setpoint spinbox, which constantly fluctuates in value.

I tested it on my setup using a laserquantum gem laser with SMD12 PSU.

[x] Bug fix
[ ] New feature
[x] Breaking change (Causes existing functionality to not work as expected) (If anybody relied on the extra information output)

[x] My code follows the code style of this project.
[x] I have documented my changes in /docs/changelog.md.
[ ] My change requires additional/updated documentation.
[x] I have updated the documentation accordingly.
[ ] I have added/updated the config example for any module docstrings as necessary.
[x] I have checked that the change does not contain obvious errors (syntax, indentation, mutable default values, etc.).
[ ] I have tested my changes using 'Load all modules' on the default dummy configuration.
[ ] All changed Jupyter notebooks have been stripped of their output cells.