Fix NSIS Template for NSIS3

[UnaNancyOwen]

NSIS2 is end of support in CPacks of CMake 3.17 or later.
We should be migrate to NSIS3 for generate PCL All-in-one Installer.

The CPack NSIS Generator now requires NSIS 3.0 or later.
https://cmake.org/cmake/help/v3.17/release/3.17.html#deprecated-and-removed-features

The template of PCL All-in-one Installer generally works as it is on NSIS2, but one error occurs with NSIS3. That means multiple definitions of "RemoveSection" macro.

# Run command: "C:/Program Files (x86)/NSIS/makensis.exe" "C:/pcl-1.11.0/build/_CPack_Packages/win64/NSIS/project.nsi"
# Output:
Processing config: C:\Program Files (x86)\NSIS\nsisconf.nsh

Processing script file: "C:/pcl-1.11.0/build/_CPack_Packages/win64/NSIS/project.nsi" (ACP)

!macro: macro named "RemoveSection" already exists!

Error in script "C:/pcl-1.11.0/build/_CPack_Packages/win64/NSIS/project.nsi" on line 182 -- aborting creation process

It is already defined in Sections.nsh of NSIS3.
Therefor, This pull request will fix by undefine "RemoveSection" macro in the first.

[kunaltyagi]

Cancelled CI manually.

@UnaNancyOwen Could you please share the steps for creating the installers on the issue tracking automating releases: #4053

[UnaNancyOwen]

Could you please share the steps for creating the installers

OK, It will take some time to put it all together.
Please give me a few days time.

[SergioRAgostinho]

Approving but I have 0 clue about anything NSIS related. :)

[kunaltyagi]

Merging because we like @UnaNancyOwen 😆