FunctionBuildDefinition: Fix docstring error (aws#8271)

Author: rbu

samcli/lib/build/build_graph.py

@@ -578,7 +578,7 @@ def __eq__(self, other: Any) -> bool:
 
 class FunctionBuildDefinition(AbstractBuildDefinition):
     """
-    LayerBuildDefinition holds information about each unique function build
+    FunctionBuildDefinition holds information about each unique function build
     """
 
     def __init__(