Update schema.xml

schema.xml version should be 1.5 now 
```
<schema name="example" version="1.5">
  <!-- attribute "name" is the name of this schema and is only used for display purposes.
       version="x.y" is Solr's version number for the schema syntax and
       semantics.  It should not normally be changed by applications.

       1.0: multiValued attribute did not exist, all fields are multiValued
            by nature
       1.1: multiValued attribute introduced, false by default
       1.2: omitTermFreqAndPositions attribute introduced, true by default
            except for text fields.
       1.3: removed optional field compress feature
       1.4: autoGeneratePhraseQueries attribute introduced to drive QueryParser
            behavior when a single string produces multiple tokens.  Defaults
            to off for version >= 1.4
       1.5: omitNorms defaults to true for primitive field types
            (int, float, boolean, string...)
     -->
```