Clean-up from recent merge of PR #3103 (#3843)

Cleaning up some unnecessary code and dependencies from the recent merge of PR #3103.
Adds missing certificate and key files to fix failures from recent merge of PR #3103.

Signed-off-by: David Venable <dlv@amazon.com>

data-prepper-plugins/aws-plugin-api/build.gradle

@@ -3,7 +3,6 @@ dependencies {
     implementation 'software.amazon.awssdk:auth'
     implementation 'software.amazon.awssdk:apache-client'
     implementation 'org.apache.httpcomponents.client5:httpclient5:5.2'
-    implementation 'com.amazonaws:aws-java-sdk-sts:1.12.395'
 }
 
 test {

data-prepper-plugins/common/src/test/resources/test_cert.crt

@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

data-prepper-plugins/common/src/test/resources/test_decrypted_key.key

@@ -0,0 +1,15 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----