Revert windows_arm64 build timeout increase (60 min -> 75 min) once arm64 build agents/builds are faster #129641

Context

windows_arm64 coreclr build jobs have been hitting the 60-minute ADO default timeout and getting canceled since ~end of May. Per @hoyosjs, the slowness comes from building the cross-arch tools needed to run crossgen (~22 -> 28 min), pushing total build time past 60 min (coinciding with the wasm build addition).

Mitigation (#129553)

Added a 75-minute timeout floor for windows_arm64 build jobs in eng/pipelines/common/global-build-job.yml. This is intentionally a crutch at the global-build-job layer rather than per-callsite (see review discussion on #129553).

Why this issue

Tracking the revert: once arm64 build-agent throughput improves or the cross-tool build is sped up, restore timeoutInMinutes: ${{ parameters.timeoutInMinutes }} in global-build-job.yml so windows_arm64 returns to the 60-min default.

Affected pipelines (empirical, public CI, last 35 days)

pgo, r2r, r2r-extra, crossgen2, crossgen2-outerloop, crossgen2-composite, crossgen2-gcstress, jitstress, jitstressregs, jitstress2-jitstressregs, jit-experimental, jitstress-isas-arm, jitstress-random, pgostress, ilasm, coreclr outerloop (ci.yml), interpreter, gc-standalone, gc-simulator, gcstress0x3-gcstress0xc, gcstress-extra.

The main runtime PR pipeline is not affected — its windows_arm64 builds already set 120-240 min.