[ios, macos] Removed MGLSource.sourceType (#6028)

Fixes #6027.

platform/darwin/src/MGLGeoJSONSource.mm

@@ -12,12 +12,9 @@
 
 @implementation MGLGeoJSONSource
 
-static NSString *MGLGeoJSONSourceType   = @"geojson";
-static NSString *MGLGeoJSONDataKey      = @"data";
-
 - (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier URL:(NSURL *)url
 {
-    if (self = [super initWithSourceIdentifier:sourceIdentifier sourceType:MGLGeoJSONSourceType]) {
+    if (self = [super initWithSourceIdentifier:sourceIdentifier]) {
         _URL = url;
         if (url.isFileURL) {
             _data = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:NULL];

platform/darwin/src/MGLRasterSource.mm

@@ -6,10 +6,8 @@
 
 @implementation MGLRasterSource
 
-static NSString *MGLRasterSourceType   = @"raster";
-
 - (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier URL:(NSURL *)url tileSize:(CGFloat)tileSize {
-    if (self = [super initWithSourceIdentifier:sourceIdentifier sourceType:MGLRasterSourceType]) {
+    if (self = [super initWithSourceIdentifier:sourceIdentifier]) {
         _URL = url;
         _tileSize = tileSize;
     }

platform/darwin/src/MGLSource.h

@@ -4,8 +4,7 @@
 @interface MGLSource : NSObject
 
 @property (nonatomic, copy) NSString *sourceIdentifier;
-@property (nonatomic, copy) NSString *sourceType;
 
-- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier sourceType:(NSString *)sourceType;
+- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier;
 
 @end

platform/darwin/src/MGLSource.mm

@@ -4,10 +4,9 @@
 
 @implementation MGLSource
 
-- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier sourceType:(NSString *)sourceType {
+- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier {
     if (self = [super init]) {
         _sourceIdentifier = sourceIdentifier;
-        _sourceType = sourceType;
     }
     return self;
 }