provider: Update Makefile fmt target to ignore ./awsproviderlint/vend…

…or (#15426)

Reference: #15391

Previously was not an issue before because we were vendoring in the root directory and explicitly referencing package subdirectories. Now that a vendor directory is included in ./awsproviderlint/ we need to exclude it. Using Makefile's built-in filter-out and wildcard functions to avoid platform specific issues with find, grep, etc.

GNUmakefile

@@ -37,7 +37,7 @@ testacc: fmtcheck
 
 fmt:
 	@echo "==> Fixing source code with gofmt..."
-	gofmt -s -w ./$(PKG_NAME) ./awsproviderlint
+	gofmt -s -w ./$(PKG_NAME) $(filter-out ./awsproviderlint/go% ./awsproviderlint/README.md ./awsproviderlint/vendor, $(wildcard ./awsproviderlint/*))
 
 # Currently required by tf-deploy compile
 fmtcheck: