UefiDevicePathLib: remove PEIM support (#449)

## Description

Removed PEIM from the list of supported modules for UefiDevicePathLib.

UefiDevicePathLib incorrectly described support for PEIM even though the
implementation for DevicePathFromHandle() uses gBS which is not
available in PEIM.

closes #306 

For each item, place an "x" in between `[` and `]` if true. Example:
`[x]`.
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- [ ] 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, ...
- [x] 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

Confirmed through CI

## Integration Instructions

PEIM Modules consuming `UefiDevicePathLib` instance of `DevicePathLib`
must use `UefiDevicePathLibBase`

MdeModulePkg/MdeModulePkg.dsc

@@ -157,16 +157,13 @@
   ExtractGuidedSectionLib|MdePkg/Library/PeiExtractGuidedSectionLib/PeiExtractGuidedSectionLib.inf
 ## MU_CHANGE - SmmLockBoxPeiLib only supports IA32 and X64.
   LockBoxLib|MdeModulePkg/Library/LockBoxNullLib/LockBoxNullLib.inf
+  DevicePathLib|MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibBase.inf
   PcdDatabaseLoaderLib|MdeModulePkg/Library/PcdDatabaseLoaderLib/Pei/PcdDatabaseLoaderLibPei.inf  # MU_CHANGE
 
 ## MU_CHANGE [BEGIN] - SmmLockBoxPeiLib only supports IA32 and X64.
 [LibraryClasses.IA32.PEIM, LibraryClasses.X64.PEIM]
   LockBoxLib|MdeModulePkg/Library/SmmLockBoxLib/SmmLockBoxPeiLib.inf
 ## MU_CHANGE [END]
-  DevicePathLib|MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibBase.inf
-
-[LibraryClasses.AARCH64.PEIM]
-  DevicePathLib|MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibBase.inf
 
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf