Bugfix: Fix Off by One Error When Creating X64 PlatformInfo.dat (#317)

## Description

AsciiSPrint() returns the string index non-inclusive of the NULL
terminator, so adding 1 to the returned string index causes a NULL byte
to be at the end of the PlatformInfo.dat file which can cause a parsing
error when interpreted in .csv format in python.

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Tested on Q35

## Integration Instructions

N/A

UefiTestingPkg/AuditTests/PagingAudit/UEFI/X64/PagingAuditProcessor.c

@@ -777,5 +777,5 @@ DumpPlatforminfo (
                   CalculateMaximumSupportAddressBits ()
                   );
 
-  WriteBufferToFile (L"PlatformInfo", TempString, StringIndex + 1);
+  WriteBufferToFile (L"PlatformInfo", TempString, StringIndex);
 }