fix(server): Bug fixes for GPTQ_BITS environment variable passthrough (#590)

# What does this PR do?

This fixes a typo and extends the GPTP_BITS environment variables
through to the second method which requires the same logic. Please let
me know if there's anything I've misunderstood in this change.

Thanks @Narsil for the original fix.

server/text_generation_server/utils/weights.py

@@ -127,8 +127,8 @@ class Weights:
                 try:
                     import os
 
-                    bits = int(os.getenv("GTPQ_BITS"))
-                    groupsize = int(os.getenv("GTPQ_GROUPSIZE"))
+                    bits = int(os.getenv("GPTQ_BITS"))
+                    groupsize = int(os.getenv("GPTQ_GROUPSIZE"))
                 except Exception:
                     raise e
             weight = (qweight, qzeros, scales, g_idx, bits, groupsize)
@@ -149,8 +149,17 @@ class Weights:
             scales = self.get_tensor(f"{prefix}.scales")
             g_idx = self.get_sharded(f"{prefix}.g_idx", dim=0)
 
-            bits = self.get_tensor("gptq_bits").item()
-            groupsize = self.get_tensor("gptq_groupsize").item()
+            try:
+                bits = self.get_tensor("gptq_bits").item()
+                groupsize = self.get_tensor("gptq_groupsize").item()
+            except SafetensorError as e:
+                try:
+                    import os
+
+                    bits = int(os.getenv("GPTQ_BITS"))
+                    groupsize = int(os.getenv("GPTQ_GROUPSIZE"))
+                except Exception:
+                    raise e
 
             weight = (qweight, qzeros, scales, g_idx, bits, groupsize)
         else: