[LLDB][NFC] Remove unneeded conditional (#138321)
we already check for `platform_sp` not null in one line below.
existing code
```
if (platform_sp) {
Status error;
if (platform_sp) {
...
...
}
}
```
`platform_sp` null check is redundant and error variable is unused.
### TEST PLAN
manual test
```
satyajanga@devvm21837:toolchain $ ./bin/lldb
LLDB logging initialized. Logs stored in: /tmp
(lldb) platform select host
Platform: host
Triple: x86_64-*-linux-gnu
OS Version: 6.9.0 (6.9.0-0_fbk5_hardened_1_gf368ae920c1a)
Hostname: 127.0.0.1
WorkingDir: /home/satyajanga/llvm-sand/build/Debug/fbcode-x86_64/toolchain
Kernel: #1 SMP Tue Feb 11 07:24:41 PST 2025
Kernel: Linux
Release: 6.9.0-0_fbk5_hardened_1_gf368ae920c1a
Version: #1 SMP Tue Feb 11 07:24:41 PST 2025
(lldb) platform process list
144 matching processes were found on "host"
PID PARENT USER TRIPLE NAME
====== ====== ========== ============================== ============================
130461 874915 satyajanga x86_64-*-linux-gnu sushd
135505 874915 satyajanga x86_64-*-linux-gnu hg.real
817146 874915 satyajanga x86_64-*-linux-gnu vscode-thrift
874915 1 satyajanga
874947 874915 satyajanga
```
and running the existing tests
```
satyajanga@devvm21837:toolchain $ ./bin/llvm-lit -v ~/llvm-sand/external/llvm-project/lldb/test/API/commands/platform/
-- Testing: 9 tests, 9 workers --
PASS: lldb-api :: commands/platform/file/read/TestPlatformFileRead.py (1 of 9)
PASS: lldb-api :: commands/platform/file/close/TestPlatformFileClose.py (2 of 9)
UNSUPPORTED: lldb-api :: commands/platform/sdk/TestPlatformSDK.py (3 of 9)
PASS: lldb-api :: commands/platform/basic/TestPlatformPython.py (4 of 9)
PASS: lldb-api :: commands/platform/basic/TestPlatformCommand.py (5 of 9)
PASS: lldb-api :: commands/platform/connect/TestPlatformConnect.py (6 of 9)
PASS: lldb-api :: commands/platform/process/launch/TestPlatformProcessLaunch.py (7 of 9)
PASS: lldb-api :: commands/platform/launchgdbserver/TestPlatformLaunchGDBServer.py (8 of 9)
PASS: lldb-api :: commands/platform/process/list/TestProcessList.py (9 of 9)
Testing Time: 13.48s
Total Discovered Tests: 9
Unsupported: 1 (11.11%)
Passed : 8 (88.89%)
satyajanga@devvm21837:toolchain $
```
