RFR: 8368975: Windows ProcessImpl.java has dead code [v2]

[Francesco Andreuzzi]

> Removal of dead code in the windows flavor of `ProcessImpl.java`. The removed branches can't be reached because `allowAmbiguousCommands` is known to be `false` in the `else` block.
> 
> Passes tier1 in GHA.

Francesco Andreuzzi has updated the pull request incrementally with one additional commit since the last revision:

  keep var

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27945/files
  - new: https://git.openjdk.org/jdk/pull/27945/files/079e2ea5..14cb9239

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27945&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27945&range=00-01

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27945.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27945/head:pull/27945

PR: https://git.openjdk.org/jdk/pull/27945