Remove FirmwareMinorVersion query for PAI

Summary:
PAI sdk does not support the `FirmwareMinorVersion` switch attribute. When querying this attribute, the SAI API returns error code.

This diff removes the `FirmwareMinorVersion` query from `fwVersionImpl()` and updates the version string format to only include the major version. The firmware version struct still populates the major version correctly.

Reference from PAI 4.0 testing:
```
s_a[0].id=172;  // FirmwareMinorVersion
rv=switch_api->get_switch_attribute(...);
// rv: fffb0000 (SAI_STATUS_ATTR_NOT_SUPPORTED)
```

Also in the pai reference guide, we see that only FirmwareMajorVersion attribute is supported

 {F1984397807}

**note: This change is limited ot SaiPhyRetimer class which is only used by ladakh**

Reviewed By: harshitgulati18

Differential Revision: D89773816

fbshipit-source-id: c48364acf0cbf8cefc67ad79c378c165f4a120d4

Author: Protick Bhowmick

fboss/lib/phy/SaiPhyRetimer.cpp

@@ -130,9 +130,7 @@ PhyFwVersion SaiPhyRetimer::fwVersionImpl() const {
   phy::PhyFwVersion fw;
   fw.version() = SaiApiTable::getInstance()->switchApi().getAttribute(
       switchId, SaiSwitchTraits::Attributes::FirmwareMajorVersion{});
-  fw.minorVersion() = SaiApiTable::getInstance()->switchApi().getAttribute(
-      switchId, SaiSwitchTraits::Attributes::FirmwareMinorVersion{});
-  fw.versionStr() = fmt::format("{}.{}", *fw.version(), *fw.minorVersion());
+  fw.versionStr() = fmt::format("{}", *fw.version());
   if (auto versionStr = fw.versionStr()) {
     XLOG(DBG5) << "fwVersionImpl switchId=" << switchId
                << ", version=" << *versionStr;