[skip ci]Update typo in search md (#13389)

Signed-off-by: Nyanliang567 <yanliang.qiao@zilliz.com>

docs/design_docs/segcore/Search.md

@@ -10,9 +10,9 @@ Search now supports two modes: json DSL mode and Boolean Expr mode. We will talk
 
 The execution mode of Boolean Expr works as follows:
 
-1. client packs search expr, topk and query vector into proto and sends to proxy node.
-2. proxy node unmarshals the proto, parses it to logical plan, makes static check, and generates protobuf IR.
-3. query node unmarshals the plan, generates an executable plan AST, and queries in the segcore.
+1. client packs search expr, topk and query vector into proto and sends to Proxy node.
+2. Proxy Node unmarshals the proto, parses it to logical plan, makes static check, and generates protobuf IR.
+3. Query Node unmarshals the plan, generates an executable plan AST, and queries in the segcore.
 
 See details of expression usage at [expr_grammar.md](https://milvus.io/docs/v2.0.0/expression.md)
 
@@ -20,7 +20,7 @@ See details of expression usage at [expr_grammar.md](https://milvus.io/docs/v2.0
 
 After obtaining the AST, execution engine uses the visitor mode to explain and executes the whole AST tree:
 
-1. Each Node includes two steps, a mandatory vector search and an optional predicate.
+1. Each node includes two steps, a mandatory vector search and an optional predicate.
 
    1. If Predicate exists, execute predicate expression stage to generate bitset as the vector search bitmask.
    2. If Predicate does not exist, vector search bitmask will be empty.