adapt min. required GJF versions in READMEs

Author: simschla

plugin-gradle/README.md

@@ -187,8 +187,8 @@ spotless {
 spotless {
   java {
     googleJavaFormat()
-    // optional: you can specify a specific version and/or switch to AOSP style
-    //   and/or reflow long strings (requires at least 1.8)
+    // optional: you can specify a specific version (>= 1.8) and/or switch to AOSP style
+    //   and/or reflow long strings
     //   and/or use custom group artifact (you probably don't need this)
     googleJavaFormat('1.8').aosp().reflowLongStrings().groupArtifact('com.google.googlejavaformat:google-java-format')
 ```

plugin-maven/README.md

@@ -213,9 +213,9 @@ any other maven phase (i.e. compile) then it can be configured as below;
 
 ```xml
 <googleJavaFormat>
-  <version>1.8</version>                      <!-- optional -->
+  <version>1.8</version>                      <!-- optional, 1.8 is minimum supported version -->
   <style>GOOGLE</style>                       <!-- or AOSP (optional) -->
-  <reflowLongStrings>true</reflowLongStrings> <!-- optional (requires at least 1.8) -->
+  <reflowLongStrings>true</reflowLongStrings> <!-- optional -->
   <!-- optional: custom group artifact (you probably don't need this) -->
   <groupArtifact>com.google.googlejavaformat:google-java-format</groupArtifact>
 </googleJavaFormat>