Fix ranged loop type in SdfLayer

[nvmkuruc]

Description of Change(s)

When building with GCC11, the following warning was observed.

 warning: loop variable ‘tokenPath’ of type ‘const std::pair<pxrInternal_v0_23__pxrReserved__::TfToken, pxrInternal_v0_23__pxrReserved__::SdfPath>&’ binds to a temporary constructed from type ‘std::pair<const pxrInternal_v0_23__pxrReserved__::TfToken, pxrInternal_v0_23__pxrReserved__::SdfPath>’ [-Wrange-loop-construct]

The value type of a std::map<TfToken, SdfPath> is std::pair<const TfToken, SdfPath> not std::pair<TfToken, SdfPath>. This change uses auto in the range loop to avoid the unnecessary temporary copy.

Fixes Issue(s)

N/A

• I have verified that all unit tests pass with the proposed changes

• I have submitted a signed Contributor License Agreement

[tallytalwar]

Filed as internal issue #USD-8137