docs: Rename IBM product name to IBM watsonx (#29802)

Thank you for contributing to LangChain!

Rename IBM product name to `IBM watsonx`

- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

docs/src/theme/ChatModelTabs.js

@@ -193,7 +193,7 @@ ${llmVarName} = AzureChatOpenAI(
     },
     {
       value: "ibm",
-      label: "IBM",
+      label: "IBM watsonx",
       text: `from langchain_ibm import ChatWatsonx
 
 ${llmVarName} = ChatWatsonx(

docs/src/theme/EmbeddingTabs.js

@@ -155,7 +155,7 @@ export default function EmbeddingTabs(props) {
       },
       {
         value: "IBM",
-        label: "IBM",
+        label: "IBM watsonx",
         text: `from langchain_ibm import WatsonxEmbeddings\n\n${embeddingVarName} = WatsonxEmbeddings(${ibmParamsOrDefault})`,
         apiKeyName: "WATSONX_APIKEY",
         packageName: "langchain-ibm",